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RK656C532    _       Mechanical  side  of  ^ 


lECHANICAL  SIDE 


OFAMTOMICALMICULATION 


ivrrrj^  ^-%r^>^  -"^'r? 


College  of  ^f)V^itim&  ant)  ^urgeong 


Mechanical  Side 

OF 

Anatomical  Articulation 


By 
GEORGE  WOOD  CLAPP,  D.D.S. 

NEW  YORK 


The  Press  of 
THE  DENTAL  DIGEST 

1910 


Copyright,  1910,  mi 

THE  DENTISTS'  SUPPLY  COMPANY 

New  York 


CONTENTS 


CHAPTEE    I. 

PAGES 

Fundamental  Considerations;  A  Definition  of  Anatomical  Articulation; 
The  Eelations  of  the  Teeth  in  Occlusion;  Positions  of  the  Teeth  in  the 
Lateral  Excursion  of  the  Mandible;     Positions  of  the  Teeth  in  Biting     .       1-15 

CHAPTEE    II. 
The  Trial  Plates 16-27 

CHAPTEE    III. 
The  Trial  Plates  as  Guides  in  Tooth  Selection 28-35 

CHAPTEE    IV. 
An  Important  Dimension  in  Artificial  Teeth 36-43 

CHAPTEE  V. 
Getting  the  exact  Dimensions  of  the  Eequired  Artificial  Teeth       .         .         .     44-55 

CHAPTEE    VI. 

Mounting  the  Trial  Plates  and  Models  on  the  Articulator;    The  Use  of  the 

Pace   Bow  56-63 

CHAPTEE    VII. 

Determining  the  Condyle  Paths;  The  Protruded  Bite;  A  Short  Cut;  Ad- 
justing  the   Condyle   Slots 64-71 

CHAPTEE    VIII. 
Working  out  the  Tooth  Curves .         .     72-78 

CHAPTEE    IX. 

Articulating  the  Teeth;  Perfecting  the  Articulation;  What  are  the  Eesults  of 
these  Steps  and  are  they  Worth  the  Trouble  Involved?;  The  Making  of 
Partial  Dentures  79-88 

CHAPTEE    X. 

Summary  of  Steps  in  Anatomically  Articulating  Pull  Dentures;  Making  the 
Trial  Plates;  Getting  the  Condyle  Paths;  Carving  the  Compensating 
Curves;    Articulating   the   Teeth 89-91 


Digitized  by  the  Internet  Archive 

in  2010  with  funding  from 

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http://www.archive.org/details/mechanicalsideofOOclap 


THE  MECHANICAL  SIDE  OF 
ANATOMICAL  ARTICULATION 

CHAPTEK    I 

FUNDAMENTAL,    CONSIDERATIONS 

When  artificial  dentures  are  anatomically  articulated*  neither  den- 
ture will  be  dislodged  during  the  act  of  crushing  food.  This  is  prob- 
ably true  in  the  fullest  sense  only  when  full  upjDcr  and  lower  plates  are 
made  together.  But  it  is  true  in  a  larger  sense  than  is  usually  taken 
advantage  of  when  partial  plates  are  made,  or  either  plate  is  made  to 
articulate  with  opposing  natural  teeth.  The  principles  of  anatomical 
articulation  may  be  applied  to  bridgework,  and  the  stress  to  which  an 
extensive  bridge  is  subjected  may  be  so  distributed  and  equalized  as 
to  greatly  lessen  the  strain  on  the  abutments. 

These  desirable  ends  may  be  attained  by  following  certain  me- 
chanical steps.  The  worker  need  not  be  a  theorist  to  attain  them,  t 
It  is  the  purpose  to  here  make  the  principles  of  anatomical  articulation 
and  their  mechanical  application  so  plain  that  any  ambitious  dentist 
can  apply  them.     The  illustrations  are  from  practical  cases. 

*  The  distinction  between  occlusion,  or  the  simple  meeting  of  the  morsal  surfaces 
of  the  teeth  of  the  upper  and  lower  sets  (something  which  may  be  secured  with  almost 
any  arrangement  of  the  teeth  of  one  set,  those  of  the  other  being  fitted  to  them), 
and  articulation,  in  which  contact  of  the  teeth  of  the  two  sets  will  occur  at  a  number 
of  widely  distributed  points  when  the  mandible  is  moved  laterally,  as  in  mastication, 
has  not  received  the  attention  that  it  should  have  done. — Snow. 

t  No  one  should  minimize  the  necessity  of  theoretical  investigations,  or  the 
credit  due  the  investigators.  Only  the  labors  of  a  long  line  of  workers,  among 
whom  Bonwill  was  a  leader,  and  of  whom  Drs.  Prothero,  Snow,  Turner,  Cross,  Grit- 
man  and  others,  yet  remain  among  us,  have  made  this  work  possible.  And  the  writer 
gladly  acknowledges  that  these  papers  are  built  almost  wholly  on  the  foundation 
these  men  have  laid.  Originality  is  here  claimed  only  as  to  the  method  of  presenta- 
tion and  a  few  mechanical  methods.  In  this  connection  many  valuable  suggestions 
have  been  received  from  Dr.  E.  S.  Ulsaver. 


]^o  other  phase  of  dental  practice  is  so  greatly  misjudged  and  under- 
estimated as  plate  work.  It  is  looked  upon  as  a  labor  which  does  not 
require  either  great  skill  or  close  attention.  Only  too  often  it  is  com- 
mitted to  unskilled  hands  or  discharged  with  a  minimum  of  attention 
by  men  who  willingly  bestow  any  amount  of  toil  in  other  departments 
of  practice. 

This  underestimation  results  wholly  from  the  lack  of  proper  knowl- 
edge concerning  the  requirements  for  and  possibilities  of  plate  work. 
No  other  phase  of  practice,  save  orthodontia  and  oral  surgery,  requires 
such  extended  knowledge  as  successful  denture  making.  Save  possibly 
in  these  two  branches,  no  other  form  of  dentistry  brings  to  the  worker 


III.  No.  1. — Diagrammatic  illustration  of  the  relations  of  the  jaws  in  occlusion.  By 
noting  the  location  of  the  vertical  black  line,  the  movements  of  the  mandible  from 
this  position  may  be  better  understood.* 


more  numerous,  more  complex  or  more  difficult  problems.  More  than 
cavity  preparation,  more  than  inlay  making,  the  making  of  dentures 
demands  knowledge  and  skill,  and  offers  opportunities  for  visible  suc- 
cess or  glaring  failure. 

The  dentist  who  has  mastered  plate  work  never  underestimates  it. 
And  when  dentists  as  a  whole  understand  that  the  present  low  estimate 

*  This  illustration  and  Nos.  7  and  9  are  published  by  courtesy  of  W.  J.  Brady, 
D.D.S. 


obtains  only  because  we,  as  a  profession,  have  neither  solved  the  prob- 
lems involved  in  anatomical  articulation  nor  grasped  the  possibilities 
it  offers,  attention  will  be  given  to  this  branch  of  dentistry  which  will 
bring  plate  work  to  its  own. 

Three  considerations  commend  the  making  of  anatomically  articu- 
lated dentures. 

The  first  is  professional.  People  who  have  lost  the  natural  teeth 
are  wholly  dependent  on  the  dentist  for  satisfactory  substitutes.  These 
are  necessary  to  proper  grinding  and  insalivation  of  food,  to  natural, 


-Full   front  view  of  two  complete   natural   dentures   with    good   articulation   save 
in   third   molars. 


easy  digestion,  to  proper  assimilation  and  energy  production.  Thus 
the  questions  of  health  and  longevity  for  many  of  our  patients  come  di- 
rectly to  our  doors. 

Only  when  edentulous  patients  are  provided  with  properly  articu- 
lated plates  can  they  properly  masticate  food.  Improperly  articulated 
plates  masticate  very  poorly,  and  digestive  troubles  usually  result. 

It  is  our  professional  duty  to  serve  these  patients  well.  It  is  pos- 
sible to  serve  them  quite  as  efficiently  as  those  who  come  for  restora- 
tion of  decayed  teeth.     Anatomically  articulated  dentures  will  enable 


such  patients  to  masticate  thoroughly  all  suitable  articles  of  food  and 
to  secure  nutriment  without  undue  strain  on  the  digestive  system.  We 
have  no  professional  right  to  neglect  such  patients  or  to  serve  them 
poorly,  when  further  knowledge  on  our  part  would  enable  us  to  serve 
them  well. 

The  second  consideration  is  physical.  It  is  closely  related  to  our 
own  health  and  the  prolongation  of  our  working  lives.  It  may  be 
summed  up  by  saying  that  the  dentist  who  alternates  well-done  plate 
work  with  operative  work  will  retain  his  physical  vigor  longer  than 
he  whose  work  is  wholly  operative.     Plate  work,  by  the  methods  to  be 


III.  No.  3. — Side  view  of  same  dentures  as  in  III.  No.  2.  Note  how  the  buccal  cusp  of 
each  upper  bicuspid  and  molar  rests  above  an  interdental  space  or  a  buccal  groove  of 
the  lowers.  In  the  mesio-buccal  cusp  of  the  upper  first  molar  this  relation  is  not  per- 
fect In  this  skull. 


described,  provides  mental  relaxation  from  the  high  nervous  tension 
of  operative  work.  And  when  anatomically  articulated  dentures  serve 
edentulous  patients  satisfactorily,  the  hours  spent  at  the  bench  will 
provide  rest,  satisfaction  and  mental  rejuvenation. 

The  third  consideration  is  financial.     Plate  work  can  be  made  as 
profitable  as  operating.     The  fees  for  plate  work  are  generally  low,  but 


they  seem  to  be  as  high  as  the  quality  of  work  warrants.  Those  den- 
tists who  make  properly  articulated  dentures,  and  add  to  their  pro- 
fessional skill  reasonable  skill  in  selling  their  services,  have  little  diffi- 
culty in  getting  remunerative  fees. 

For  the  dentist  who  is  now  making  dentures  in  the  ordinary  man- 
ner and  is  receiving  unsatisfactory  fees,  an  attractive  future  is  open. 
If  he  will  anatomically  articulate  dentures  for  appreciative  patients, 


'''''■  No!!:  ht^^^T^/'T  "*'  °^'"'''  "^"'"'^  exhibiting  practically  perfect  articulation. 
Note  how  perfectly  the  upper  buccal  cusps  close  over  the  interdental  spaces  or  buccal 
grooves  of  the  lowers.* 


he  will  find  his  hours  at  the  bench  as  remunerative  as  those  spent  at 
the  chair. 


A    DEFINITION-    OF    ANATOMICAL    ARTICULATION 

Before  we  can  enter  upon  the  detailed  study  necessary  to  anatomi- 
cally articulate  dentures,  we  must  have  a  definition  of  what  anatomical 
articulation  is.  While  many  definitions  are  possible,  the  following  is 
free  from  technical  difficulties,  and  seems  to  meet  all  requirements. 

*  This  photo  and  Nos.  5  and  6  are  from  Turner's  Prosthetic  Dentistry,  and  are 
reproduced  by  the  courtesy  of  Messrs.  Lea  &  Febiger,  Philadelphia,  Publishers. 


6 

"  Artificial  dentures  are  anatomically  articulated  when  they  ex- 
hibit the  characteristics  of  articulation  common  to  the  best  natural 
dentures." 

It  is  evident,  then,  that  we  should  get  our  detailed  information  as 
to  what  anatomical  articulation  is  by  studying  the  best  obtainable 
specimens  of  natural  dentures.  Good  natural  dentures  are  rare.  A 
noted  plate  worker,  who  has  made  a  study  of  articulation,  says  that 
in  forty  years  of  practice  he  has  seen  only  three  dentures  which  he 


III.  No.  5. — Lingual  view  of  two  perfect  human  dentures.  Note  how  the  upper  lingual 
cusps  fit  into  the  fossce  and  interdental  spaces  of  the  lower  teeth.  It  Is  this  close  adapta- 
tion which  is  desired  as  the  first  requisite  in   artificial  teeth. 


regarded  as  practically,  perfect.  An  examination  of  over  1,500  skulls 
in  the  Museum  of  ISTatural  History,  City  of  'New  York,  revealed  only 
three  dentures  likely  to  be  of  value  as  subjects  of  study. 

Three  great  facts  characterize  perfect  natural  dentures.  They  may 
be  stated  in  advance,  to  be  studied  in  detail  later.     They  are : 

1.  When  the  mandible  is  thrown  to  one  side  and  brought  into  con- 
tact with  the  upper  teeth,  the  lower  teeth  are  in  contact  with  the  uppers 
at  three  widely  separated  points.  On  the  side  engaged  in  crushing 
the  food,  the  lower  teeth  from  central  to  third  molar  are  in  contact  with 
the  opposing  uppers.     The  lower  third  molar  on  the  opposite  side  is 


in  contact  with  the  upper  second  molar.  In  artificial  dentures  this 
form  of  contact  prevents  dislodgment  of  either  plate  and  permits  the 
exertion  of  an  amount  of  force  otherwise  impossible.  It  has  been  erro- 
neously styled  ''  three  point  contact,"  but  there  is  contact  at  more  than 
three  points. 

2.  When  the  teeth  are  in  lateral  occlusion,  the  buccal  cusps  of  the 
lowers  are  laterally  in  line  with  the  buccal  cusps  of  the  uppers.  The 
lingual  cusps  of  the  lowers  are  in  line  with  the  lingual  cusps  of  the 


iLli.  No.  6. — On  the  left,  balf  of  a  lower  natural  denture.  On  the  right,  half  of  the 
upper  denture  opposed  to  this  lower.  Arrows  lead  from  the  cusps  of  one  set  to 
the  fossa  or  interdental  space  Into  which  that  cusp  closes  in  a  position  of  central 
occlusion. 


uppers.  The  sulci  and  fossse  of  the  opposed  occlusal  surfaces  form  a 
space  known  as  the  rectangular  groove.  In  this  groove  the  food  is 
compressed. 

3.  The  food  in  the  rectangular  groove  is  finally  crushed  by  the 
mandible  sliding  toward  the  median  line.  The  buccal  cusps  of  either 
set,  on  the  side  engaged  in  crushing,  slide  through  the  spaces  between 
the  teeth  of  the  other  set,  or  through  buccal  grooves.  This  relation  of 
cusps  to  grooves,  with  the  aid  of  the  articulating  molars  on  the  oppo- 
site side  of  the  mouth,  prevents  the  dislodgment  of  dentures  made  on 
this  principle. 

The  lingual  cusps  move  through  interdental  spaces  or  lingual 
grooves  in  a  similar  manner. 


THE  RELATIONS  OF  THE  TEETH  IN  OCCLUSION 

Illustrations  1,  2,  3  and  4  illustrate  two  well-articulated  natural 
dentures  in  position  of  occlusion.  This  is  the  position  from  which  the 
mandible  starts  on  its  lateral  excursion,*  and  the  position  in  which  it 


III.  No.  7. — Diagrammatic  illustration  showing  the  lateral  movement  of  the  mandible.  The  man- 
dible has  moved  downward,  sideways  and  upward,  and  is  now  ready  to  begin  the  final  crushing 
movement.  The  buccal  cusps  of  the  bicuspids  and  molars  on  the  right  side  are  in  the  same 
vertical  plane  and  interdigitated.  The  final  crushing  movement  will  be  accomplished  by  the 
sliding  of  the  mandible  back  to  a  position  of  occlusion.  This  distance  is  shown  by  the  offset  in 
the  vertical  line.f 


rests  at  the  end  of  the  triturating  movement.     We  can  arrive  at  some 
valuable  data  by  a  study  of  the  occlusion  as  here  exhibited. 

It  will  be  seen  that  the  upper  teeth  bite  outside  of  the  lowers.  This 
overbite  serves  to  keep  the  tissues  of  the  cheeks  from  between  the  teeth, 
and  is  part  of  the  mechanism  by  which  Nature  secures  proper  crush- 
ing of  the  food.  Beginning  with  the  first  bicuspid  and  extending  back 
to  the  third  molar,  the  occlusal  surfaces  of  the  upper  teeth  show  a  con- 

*  It  is  quite  possible  that  the  normal  position  of  the  jaws  in  life  during  periods 
of  rest  is  with  the  teeth  slightly  separated.  They  are  probably  brought  together  only 
as  the  result  of  nervous  impulses. 

t  Shown  by  the  courtesy  of  W.  J.  Brady,  D.D.S. 


9 

tinuous  groove,  narrow  in  some  places  and  wide  in  others.  Into  this 
groove  the  buccal  cusps  of  the  lower  bicuspids  and  molars  fit.  When 
the  teeth  have  been  slightly  worn  by  the  processes  of  mastication,  the 
fit  of  the  cusps  into  the  sulci  and  fossae  of  the  opposing  teeth  is  nearly 
perfect. 

The  occlusal  surfaces  of  the  lower  bicuspids  and  molars  beginning 


''''", fm^lwhT?*"''^  f""'"*''  '°  '""'"'*°  illustrated  diagrammatieally  in  Illustration   No.    7.     Seen 

TcaT  1  .rofT"-     f '"  'T  "'"'*  '"'"^^  ''^'^'"^''^'  '"*''  ^-^--  --^  *°  ^'--  contact    t^e 
buccal    CU.PS    of   tUe   posteriors    being   interdigitated.      The   lower    left    third    molar   is    in    contact 

with  the  upper  left  second  molar,  establishing  balance.     The  teeth  are  considerably  worn  bTuseJ 


with  the  second  bicuspid,  show  a  similar  groove,  and  into  this  groove 
the  lingual  cusps  of  the  upper  bicuspids  and  molars  fit. 

POSITIONS    OF    THE    TEETH    IN    THE    LATEEAL    EXCURSION    OF    THE 

MANDIBLE 

When  the  jaw  starts  on  that  movement  which  is  to  end  in  the  trit- 
urating of  food,  it  moves  downward  and  to  the  right  (or  perhaps  to 
the  left).  It  thus  separates  the  occlusal  surfaces  of  the  teeth  and  into 
the  space  thus  provided  the  cheek  and  tongue  thrust  the  food  to  be 
triturated.  The  mandible,  still  held  to  the  side,  moves  upward  and 
comes  in  contact  with  the  upper  jaw  in  such  position  that  the  buccal 
cusps  of  the  lower  bicuspids  and  molars,  on  the  side  engaged  in  crush- 


10 

ing  food,  are  in  nearly  the  same  vertical  plane  with  the  corresponding 
cusps  of  the  upper  teeth,  and  interdigitated  with  them.  This  contact 
is  often  continuous  from  the  lower  left  and  upper  right  centrals  to 
the  third  molars  of  both  sets.*  So  close  is  the  adaptation  of  the  upper 
and  lower  buccal  marginal  ridges  that  the  escape  of  any  large  particles 
of  food  from  between  the  occlusal  surfaces  of  the  teeth  is  prevented. 
Similar  adaptation  of  the  lingiial  cusps  of  the  upper  and  lower  teeth 
largely  prevents  escape  of  food  in  that  direction.  The  food  thus  locked 
in  position  is  ready  for  the  final  triturating. 

This  is  accomplished  by  the  sliding  of  the  mandible  toward  the  me- 
dian line  of  the  head  until  it  cOmes  to  rest  with  the  buccal  cusps  of  the 
lower  bicuspids  and  molars  in  the  foss^  of  the  uppers. f  In  sliding 
thus  back  to  place,  each  cusp  of  each  posterior  tooth  passes  through  its 
appropriate  groove  or  interdental  space  in  the  opposing  set. 

By  this  motion  of  the  teeth  the  food  is  finely  crushed. :{: 

Meantime,  on  the  other  side  of  the  jaw  an  important  adaptation  has 
occurred.  The  downward  and  sideways  swing  of  the  mandible  brought 
the  lower  left  third  molar  forward  and  inward.  When  the  uj)ward 
move  of  the  mandible  brought  the  teeth  on  the  crushing  side  into  con- 
tact, the  buccal  cusps  of  the  lower,  third  molar  came  into  contact  with 
the  lingual  cusp  of  the  upper  left  second  molar.  This,  like  the  con- 
tact on  the  crushing  side,  is  a  sliding  contact.  It  is  made  at  the  same 
time  as  the  contact  on  the  crushing  side,  and  is  maintained  in  the  same 
manner  throughout  the  crushing  movement.  It  has  great  value.  The 
force  often  required  to  crush  food§  is  so  distributed  by  this  "  balancing 
contact  "  that  all  tendency  to  tilt  or  twist  the  mandible  is  obviated. 
The  mandible  is  in  sliding  contact  with  the  upper  jaw  at  the  three  most 
widely  separated  points,  at  the  lower  left  third  molar  and  continuously 
from  the  lower  centrals  to  the  right  third  molar. 

As  the  mandible  is  thus  relieved  of  all  tendency  to  tilt,  the  power 
ful  temporal  and  masseter  muscles  of  both  sides  are  free  to  asist  in 

*  It  is  not  the  intention  to  here  enter  into  a  consideration  of  the  Curve  of  Spee 
and  the  lateral  curve  which  make  these  relations  possible,  but  merely  to  outline  what 
the  relations  are. 

t  This  final  triturating  movement  is  very  short,  probably  not  greater  than  half 
the  width  of  the  occlusal  surface  of  the  upper  first  bicuspid  at  the  position  of  that 
tooth.  Dr.  J.  Leon  Williams  believes  it  to  be  very  much  less  than  that,  perhaps  not 
more  than  one  one-hundredth  of  an  inch. 

t  The  writer  suggests  that  the  upward  movement  of  the  mandible,  which  crushes 
the  food,  be  known  as  ' '  the  crushing  movement, ' '  and  the  final  movement  as  ' '  the 
triturating  movement."  Of  course  these  terms  are  for  descriptive  use,  since  the 
movement  is  really  all  one. 

§  For  some  common  articles  of  food  a  crushing  force  of  200  pounds  is  required. 


11 

the  crushing  of  food  on  either  side.  The  crushing  power  is  thereby 
greatly  increased. 

A  realization  of  the  importance  of  this  balancing  contact  will  be  of 
great  value  to  the  plate  worker. 

Having  sketched  in  outline  the  positions  of  the  teeth  in  occlusion 
and  in  the  crushing  and  triturating  movements,  let  us  examine  their 
relations  in  the  act  of  biting. 

POSITIONS    OF    THE    TEETH    IN    BITING 

Food  is  bitten  with  the  incisors.  It  should  be  triturated  with  the 
bicuspids  and  molars. 

To  bite  oft"  food  the  mandible  moves  downward  and  forward  from 


III.   No.   9. — Diagram  illustrating  ttie  forward  movement  of  the  mandible  to  produce  the  end  to  end 
bite.     When  the  mandible  is  in  central  occlusion,   the  vertical  black  line  is  continuous.* 


its  position  of  rest,  and  then  upward,  the  lower  incisors  coming  into 
contact  with  the  uppers  in  a  protruded  position.  This  protrusion 
varies  in  different  cases.  Its  possible  range  varies  considerably  in  any 
normal  mouth. 

Probably  the  most  common  form  of  incisive  bite  is  for  the  cutting 

*  Shown  by  the   courtesy   of   W.   J.   Brady,  D.D.S. 


12 

edges  of  the  upper  and  lower  incisors  to  come  into  end-to-end  contact. 
To  complete  the  biting  movement  the  lower  incisors  slide  backward 
and  upward  against  the  lingual  surfaces  of  the  uppers,  shearing  off  the 
food. 

When  the  upper  and  lower  incisors  are  widely  separated,  there  is 
no  contact  between  the  posterior  teeth.* 

When  the  cutting  edges  of  the  incisors  come  into  contact,  the  pos- 


III.  No.  10. — Same  natural  dentures  as  in  Nos.  2,  3,  and  8.  Here  shown  in  extreme  pro- 
trusion bite.  Lower  incisors  well  in  front  of  uppers.  Buccal  cusps  of  both  dentures 
in  contact.  The  mandible  is  protruded  farther  than  customary  in  incising.  The 
"  shearing  oft  "  movement  can  be  accomplished  only  by  the  mandible  sliding  backward 
till  the  lower  incisors  are  slightly  behind  the  uppers,  and  then  upward.  At  the  same 
time  all  other  teeth  slide  to  occlusion. 


terior  teeth  are  in  contact  throughout  the  range  of  both  dentures,  though 
the  form  of  contact  is  quite  different  from  that  maintained  during  the 
crushing  movement.  In  many  cases,  at  least,  the  mandible  moves  for- 
ward about  half  the  mesio-distal  width  of  a  bicuspid  to  establish  the  end- 
to-end  bite  of  the  incisors.     The  buccal  cusp  of  the  upper  first  bicuspid 


*  The  patient  wearing  artificial  dentures  must  prevent  dislodgment  during  their 
complete  separation  by  not  taking  too  large  bites,  and  by  pushing  inward  on  the  food 
while  the  teeth  bite  it  off. 


13 


will  then  be  found  directly  above  the  buccal  cusp  of  the  lower  second 
bicuspid,  as  shown  in  the  illustrations  herewith. 

This  contact  throughout  both  sets  is  attained  by  the  peculiar  antero- 


rLL.  No.  11. — Two  excellent  natural  dentures  in  occlusion.  The  separation  between  the  upper  cen- 
trals is  congenital  and  is  equalled  by  the  spaces  between  the  lower  centrals  and  laterals.  The 
dentures  are  complete,  are  practically  unworn,  and  exhibit  no  decay.  The  occlusion  is  ex- 
cellent. 


posterior    curve    of  the  occlusal  surfaces,  known  as  the  Compensating 
Curve  or  the  Curve  of  Spee. 

The  sliding  backward  and  upward  of  the  lower  incisors,  to  com- 
plete the  incisive  or  shearing  movement,  is  made  possible  by  the  simul- 


14 

taneous  sliding  of  all  other  cusps  on  the  inclined  planes  of  the  oppos- 
ing teeth  to  again  occupy  the  position  of  rest. 

What  does  this  advance  reading  show  us  ? 

It  gives  us  our  first  glimpse  of  the  mechanical  plans  underlying  the 


III.  No.  12. — The  mandible  thrown  forward  in  end-to-end  bite.  Tlie  cusp  of  the  upper  cuspid  is 
above  and  in  contact  with  the  cusp  of  the  lower  first  bicuspid.  Practically  similar  opposition  of 
upper   and   lower   buccal   cusps   obtains   throughout   the   range   of   both   dentures. 


articulation  of  good  natural  dentures  in  such  way  that  we  may  apply 
the  same  principles  to  the  articulation  of  artificial  dentures. 

We  see,"  first,  that  in  the  position  of  direct  occlusion  and  that  of 


15 

lateral  occlusion  the  teetH  interdigitate  with  almost  the  accuracy  of 
gear  teeth.  We  see  also  that  in  all  positions  where  great  force  is  to 
be  exerted,  the  mandible  lies  in  contact  with  the  upper  denture  at  three 
or  more  widely  separated  points.  By  thus  supporting  the  mandible 
against  tipping,  it  is  possible  for  the  temporal  and  masseter  muscles 
of  both  sides  to  exert  their  power  in  the  final  biting  or  shearing  move- 
ment, and  in  the  final  crushing  movement.  The  power  of  the  jaw  is 
thus  greatly  increased  over  that  which  would  result  from  the  pull  of 
only  one  set  of  these  muscles. 

Great  as  are  the  advantages  of  these  mechanical  arrangements  to  the 
natural  denture,  those  resulting  from  similar  articulation  of  artificial 
dentures  are  greater.  The  teeth  of  the  natural  denture  cannot  be  easily 
dislodged,  but  if  the  artificial  dentures  are  poorly  articulated,  they  may 
be  so  easily  dislodged  as  to  make  mastication  impracticable. 

When,  however,  artificial  dentures  are  made  on  the  principles  of 
which  we  have  here  caught  the  first  glimpse,  they  are  very  stable  as  to 
position,  and  they  make  possible  the  exercise,  in  biting  and  grinding, 
of  forces  wholly  impossible  otherwise. 


CHAPTEE   II 


THE    TEIAL    PLATES 


We  have  now  learned  what  are  the  characteristics  of  articulation  as 
exhibited  by  the  best  natural  dentures,  and  may  proceed  with  those 
steps  which  will  reproduce  such  articulation  in  the  artificial  dentures. 

Good  dentures  presuppose  good  impressions  and  good  models  of 
both  jaws.* 

Over  each  model  a  base  plate  of  base-plate  composition  should  be 
shaped  and  trimmed  to  approximately  the  area  the  ]3late  is  to  occupy. 
These  base  plates  might  be  made  of  wax  or  of  modeling  comjjosition, 
but  the  manipulation  to  which  they  are  to  be  subjected  makes  it  advis- 
able that  base-plate  composition  be  used.  This  can  be  obtained  at  any 
dental  depot.  It  is  easily  shaped  when  warm  and  very  stable  when 
cold.  It  may  be  accurately  adapted  to  the  model,  permits  getting  suc- 
tion under  the  upper  trial  plate  and  assists  in  making  a  thin  and  even 
denture  over  the  vault. 

When  this  base  plate  has  been  adapted  to  the  upper  model  and 
trimmed  to  approximate  shape,  it  is  transferred  to  the  mouth  and  fitted 
just  as  a  gold  base  would  be.  It  should  be  as  high  all  round  as  may 
be  without  being  displaced  by  the  downward  pull  of  the  muscles,  f  The 
retention  may  sometimes  be  greatly  increased  by  making  the  rim  high 
from  the  second  bicuspids  to  the  heels. 

The  upper  base  plate  is  left  in  this  condition  while  a  step  slightly 
in  anticipation  of  our  immediate  requirements  is  taken.  That  step  is 
to  draw   on  the   patient's  face,  by  the  aid  of  a  ruler,  a  line  from  the 

*It  is  assumed  that  full  upper  and  lower  dentures  for  one  mouth  are  being 
made  together. 

t  The  height  may  be  determined  by  trying  the  base  plate  in  the  mouth  and  then 
pulling  the  cheeks  and  lips  downward.  The  sides  should  be  trimmed  until  the  base 
cannot  be  dislodged  in  this  manner.  There  should  be  good  clearance  at  the  frenum 
and  at  the  buccal  strings. 


17 

lowest  point  of  the  external  auditory  meatus*  to  the  lowest  point  of  the 
ala  of  the  nose.  This  line  may  be  seen  in  Illustration  No.  13.  Its 
use  will  be  shown  presently. 


III.   No.   13. — Making  pressure  on   the  knife  blade  to   bring  it  parallel  with   the  line  on   the  face. 
This  determines  the  occlusal  plane  of  the  bites. 


Any  moisture  present  on  the   upper  base  plate  is  now  dried.     A 
sheet  of  base  plate  wax  is  cut  to  about  two-thirds  its  usual  length  and 


The  external  opening   of  the  canal  to  the  middle  ear. 


18 

heated  on  one  side  till  the  wax  begins  to  run,  when  the  softened  side  is 
doubled  on  itself.  One  side  of  the  folded  sheet  is  now  heated  in  like 
manner  and  again  folded  on  itself,  forming  a  roll.     The  roll,  still  soft. 


III.  No.  14. — Occlusal  planes  of  bites  established  parallel  with  line  from  lower  margin 
of  auditory  meatus  to  lower  margin  of  ala  of  nose.  Blade  of  knife  held  between  bites ; 
handle  projecting. 


is  aligned  along  the  upper  ridge  and  quickly  and  firmly  attached  with 
the  aid  of  a  hot  spatula.  The  base  plate,  with  the  wax  rim  attached, 
will  be  referred  to  hereafter  as  the  trial  plate. 


19 

A  silver. table  knife  is  now  laid  within  reach  of  the  right  hand. 
While  the  wax  ridge  is  yet  soft,  the  trial  plate  is  j^laced  in  the  month 
and  supported  by  the  pressure  of  the  fourth  finger  of  the  left  hand  in 
the  vault.  The  blade  of  the  table  knife  is  laid  along  the  ridge  on  the 
right  side,  from  heel  to  median  line,  and  supported  firmly  in  position 
by  the  middle  and  forefingers  of  the  left  hand.     With  the  right  hand, 


ILJ..   No,    15.-^Uppier   trial   plate    (iuv^rt^d)    with   the   proper  occlusal   plane  established   on   one   side. 


elevate  or  depress  the  projecting  portion  of  the  knife  until  it  is  seen  to 
be  parallel  with  the  line  drawn  on  the  face.  It  is  not  expected  that 
the  knife  will  continue  this  line,  since  it  is  naturally  below  it,  but  that 
it  will  be  parallel  with  it. 

The  pressure  of  the  knife  on  the  still  soft  wax  of  the  ridge  will 
flatten  the  occlusal  surface,  as  in  Illustration  jSTo.  15,  and  align  it  par- 
allel with  the  line  drawn  on  the  face.  To  get  this  surface  parallel  with 
this  line  was  the  object  sought  when  using  the  knife.  This  surface  of 
this  ridge  will  later  be  carved  so  that  it  will  no  longer  be  flat,  but  the 
accuracy  of  the  future  work  will  be  greatly  aided  by  getting  this  oc- 
clusal surface  into  the  proper  plane  at  this  time.  The  trial  plate  should 
now  be   removed   from   the   mouth    and   the   occlusal   surface    of  the 


20 

ridge  on  the  left  side  trimmed  to  correspond  with  that  on  the  right. 
The  ujjper  trial  plate,  thus  trimmed,  is  put  back  into  the  mouth,  and 
the  lips  are  brought  together  lightly  in  repose.  This  position  oi  the 
lips  is  shown  in  Illustration  ^o.  20.  An  instrument  is  now  placed  be- 
tween the  lips  and  a  horizontal  line  is  marked  on  the  labial  surface  of 
the  upper  trial  plate.  This  mark  i&^nown  as  the  "rest  line"  from 
the  resting  position  of  the  lips.*     See  Illustration  JSTo.  17.     The  trial 


III.  No.  16. — Section  of  an  upper  trial  plate  at  the  median  line,  trimmed  labially 
and  occlusally  as  required  for  the  case  in  which  it  was  used.  Shows  form 
of  ridge. 


plate  is  now  removed  from  the  mouth  and  a  parallel  horizontal  line  is 
made  about  1%  millimeters  (approximately  one-sixteenth  inch)  below 
the  rest  line,  and  the  wax  is  trimmed  vertically  to  this  mark.  Care 
must  be  exercised  to  maintain  the  occlusal  plane  already  established. 
Should  the  upper  trial  plate  be  shorter  than  would  be  indicated  by  the 
above  measurements,  it  must  be  built  down,  maintaining  the  occlusal 
plane  while  so  doing. 

When  experience  makes  it  possible,  it  will  be  found  practicable  to 
press  the  knife-blade  upward  till  the  ridge  is  but  little  deeper  than  the 
upper  lip  is  long.     Very  little  vertical  trimming  will  then  be  necessary. 

The  upper  trial  plate,  trimmed  to  correct  length,  is  left  in  the  mouth, 

*  The  lips  are  said  to  touch  lightly  in  repose  when  it  does  not  require  effort  to 
get  them  together,  and  when  they  do  not  touch  so  heavily  as  to  be  unduly  turned  out 
at  the  margins. 


21 

while  a  roll  of  wax  is  shaped  and  attached  to  the  lower  base  in  the  same 
manner  as  was  done  to  the  upper.     This  is  shaped  to  be  deeper  verti- 


III.    No.   17. — Marking  the  "rest  line.' 


cally  than  the  finished  ridge  will  be.     While  the  ridge  is  still  soft,  this 
lower  trial  plate  is  put  into  the  mouth  and  the  jaws  closed  together 


22 

until  the  lips  lightly  touch  in  repose.     By  a  little  practice,  this  may  be 
successfully  done,  especially  if  the  patient  is  not  allowed  to  approximate 


III.  No.  18. — Edentulous  patient  seen  from  the  side.  The  sinking  of  the  lips  as  well  as  the  ver- 
tical droop  is  here  clearly  seen,  especially  at  the  corner  of  the  orifice  of  the  mouth.  (This 
picture  and  No.  20  were  taken  in  the  same  light  and  at  nearly  the  same  time.  They  illustrate 
the  necessity   for   and   possibility  of  restoration.) 


the  jaws  too  rapidly.  When  the  lips  are  in  correct  position  the  lower 
ridge  will  be  of  the  right  height  and  will  have  its  occlusal  surface  in 
the  proper  plane. 


23 


The  combined  height  of  the  trial  plates  will  be  found  unevenly  di- 
vided, the  upper  bite  being  much  higher  than  the  lower.     This  is  be- 


ILL.  No.  19. — Edentulous  patient  showing  drooping  of  soft  tissues  following  extraction  of  teeth. 
The  labial  ends  of  the  alse  and  septum  droop  and  the  tissues  in  the  labial  triangle  sink  Inward. 
(This  picture  and  No.  21  were  taken  in  the  same  light  at  the  same  time,  and  illustrate  very 
clearly  the  possibilities  in  restoration.) 


cause  these  plates  are  designed  to  fix  the  positions  of  the  upper  teeth 
rather  than  of  the  lowers.  When  the  upper  teeth  are  set,  the  lowers 
may  be  set  to  them,  underbiting  them  in  the  anteriors,  and  interdigitat- 
ing  with  them  in  the  posteriors.     In  most  natural  dentures,  nature  ex- 


24 

tends  the  upper  centrals  below  the  rest  line.  By  doing  so  she  enhances 
the  beauty  of  the  expression  when  the  lips  are  slightly  separated,  as  is 
common  in  periods  of  relaxation;  and  she  maintains  for  the  edge  of 


III.  No.  20.- — Patient  with  bites  in  position.  The  labial  ends  of  the  alse  and  septum  are  pushed 
up  to  place,  vivifying  the  expression.  The  lips  are  built  out  in  harmony  with  the  general  facial 
contour.     Note  how  much  more  animated  and  vigorous  the  expression  is  than  in  No.   17. 


the  lower  lip,  when  the  lips  are  closed,  that  outward  turn  which  con- 
tributes so  materially  to  facial  expression  and  often  to  beauty.  The 
fact  that  the  lower  trial  plates  are  shorter  than  the  lower  teeth  are  to  be, 


25 

need  cause  us  no  uneasiness,  since  it  will  be  remedied  when  the  lower 
teeth  are  set  to  underbite  the  uppers. 

ISTow  that  the  ridges  are  of  correct  heights,  the  trimming  or  build- 
ing of  the  labial  and  buccal  surfaces  to  give  the  desired  facial  expres- 


ILL.  No.  21. — Patient  with  trial  plates  properly  built  up  and  out  as  in  111.  No.  22.  The  tissues  in  tW 
labial  triangle,  the  alse  and  septum,  and  the  corners  of  the  orifice  of  the  mouth  have  been  lifted 
by  maliing  the  plate  high  over  the  cuspid  eminence.     Contrast  the  appearance  here  and  in  No.   IS 


sion  may  be  done.  While  doing  this  trimming  the  dentist  will  havv 
opportunity  to  exercise  his  artistic  ability  in  restoring  the  expression 
of  the  face.     Following  the  extraction  of  the  upper  cuspids,  the  outer 


26 

plate  of  the  alveolus  sinks  and  the  soft  tissues  fall  not  only  inward  but 
downward.     See  Illustrations  JSTos.  18  and  19. 

Much  of  the  loss  of  habitual  expression  may  be  restored  by  lifting 
the  tissues  vertically.*     The  effect  of  such  lifting  on  the  expression  of 


III.  No.  22. — Upper  and  lower  trial  plates  with  occlusal  iilaue  properly  established  and  built  out 
labially  and  buccally  to  give  proper  expression.  The  upper  is  as  high  over  the  cuspid  eminence 
as  can  be  worn  and  lifts  the  tissues,   as  in  Illustrations   Nos.    18  and   19. 


any  patient  may  be  seen  by  placing  a  dull  bladed  instrument  under  the 
lip  of  an  edentulous  person  and  pressing  upward.  The  facial  ends  of 
the  septum  and  of  the  ala,  together  with  the  tissues  which  form  what 
might  be  called  "  the  labial  triangle/'f  may  be  lifted  toward  the  eye. 
By  this  lifting,  the  "  drooping "  expression  so  common  to  edentulous 
faces  may  be  largely  done  away,  to  the  great  advantage  of  the  patient.:}: 
See  Illustrations  ISTos.  20  and  21.  If  the  upper  base  be  trimmed  high 
over  the  cuspid  eminences  and  as  high  from  these  to  the  frenum  as  may 

*  This  means  vertically  when  the  head  is  upright. 

t  That  triangle  formed  by  the  ala  of  the  nose  and  the  line  from  the  ala  to  the 
corner  of  the  orifice  of  the  mouth,   and  spreading  into  the  lip  below. 

t  The  writer  is  glad  to  acknowledge  his  indebtedness  to  Dr,  A.  O.  Hunt  for  in- 
struction on  this  point. 


27 

be  without  dislodgment  of  the  trial  plate  by  the  mu&cles,  this  lifting 
maj  be,  at  least  in  part,  accomplished. 

The  distinction  must  be  kept  in  mind  between  a  high  trial  plate 
in  this  section  and  a  thick  one.  A  trial  plate  is  high  vertically ;  in  this 
section  it  would  be  thin  from  jaw-bone  to  lip.  It  will  be  frequently 
necessary  to  carve  the  trial  plate  as  thin  in  this  section  as  the  plate  can 
safely  be.  The  trial  plates  for  the  case  here  illustrated  are  shown  in  Il- 
lustration ISTo.  22. 

When  making  plates  without  anterior  gums  it  will  often  be  found 
advisable  to  have  a  horn  of  rubber  reach  forward  from  where  the  gums 
begin  and  lift  the  soft  tissues  over  the  cuspid  eminence. 

The  guide  as  to  the  fullness  of  the  lips  and  cheeks  is  found  in  the 
expression,  and  the  trial  plates  should  be  built  or  carved  as  may  be 
shown,  by  trial  in  the  mouth,  to  most  favorably  aifect  that  expression. 


CHAPTEK    III 

THE    TKIAL    PLATES    AS    GUIDES    IN    TOOTH    SELECTION 

While  the  most  important  function  of  the  trial  plates  is,  of  course, 
to  determine  the  relation  of  th6  jaws,  their  aid  in  the  correct  selection 
of  the  teeth  is  scarcely  less  important.  This  function  of  the  trial  plates 
seems  to  have  been  but  little  appreciated  in  the  past  and,  so  far  as  the 
writer  knows,  has  never  been  properly  developed. 

A  little  consideration  shows  that  both  the  mechanical  and  the  ar- 
tistic success  of  the  plates  are  largely  dependent  on  teeth  of  proper  size 
and  form  being  selected.  There  is  no  other  guide  to  the  selection  of 
the  proper  teeth  save  correctly  made  and  properly  articulated  trial 
plates.  By  means  of  them,  the  dimensions  of  the  required  teeth  may 
be  obtained  with  surprising  ease,  accuracy  and  rapidity,  once  the  very 
simple  technic  is  mastered. 

Do  not  think  such  selection  is  opposed  to  the  exercise  of  taste  and 
art  in  the  choice  of  teeth.  Most  assuredly  it  is  not.  Such  selection 
assists  art  in  a  most  valuable  manner.  Art  in  tooth  selection  deals  first 
with  the  form  and  color  of  the  teeth  and  later  with  their  arrangement. 
It  is  practically  impossible  to  determine  by  the  precepts  of  art  alone 
the  exact  dimensions  of  the  teeth  required  for  a  denture.  But  me- 
chanics will  give  the  exact  dimensions  very  quickly  and  very  accurately ; 
and  art,  using  these  dimensions  as  the  beginning  of  its  work,  determines 
the  outline  of  the  teeth  and  their  shade. 

Art  need  have  no  hesitation  in  availing  herself  of  the  services  of  her 
humble  and  necessary  handmaid — Mechanics,  for  if  Mechanics  build 
the  foundation,  Art  rears  the  superstructure  and  beautifies  it.  As  it 
avails  little  to  beautify  a  superstructure  which  stands  awry,  so  art  in 


29 

plate  work,  without  a  foundation  of  sound  mechanics,  avails  little.     Of 
what  use  are  artistic  plates  that  will  not  masticate? 

Ui3on  the  trial  plates  thus  properly  carved  for  height  and  fullness, 
we  have  now  to  record  the  dimensions  of  the  teeth  indicated  for  the 
case  in  hand.  This  may  be  easily  done  by  observing  the  rather  con- 
stant   relations   between   the   positions  of  the  lips  and  the  sizes  of  the 


III.  No.  23. — The  incisal  edges  of  the  upper  centrals  normally  project  about  IJ  mm.  below 
the  rest  line  of  lips.  Cardboard  placed  between  lips  at  rest.  Lips  opened.  Location 
of  rest  line  on  natural  centrals  shown  by  end  of  cardboard. 


natural  teeth  in  the  majority  of  normal  mouths.  Even  were  no  such 
relations  observable,  the  following  method  would  still  greatly  aid  in  ob- 
taining artistically  pleasing  results  with  a  minimum  expenditure  of 
time  and  labor. 

It  has  been  noted  that  about  three  persons  out  of  four,  when  smil- 
ing unobserved,  raise  the  upper  lip  until  its  edge  is  on  a  level  with  the 


30 

necks  of  the  natural  centrals.     The  effect  thus  produced  is  very  pleas- 
ing, much  more  so  than  in  those  cases  where  the  lip  is  not  raised  to 
the  necks  of  the  teeth  or  is  raised  much  above  them.     Profiting  by  this- 
observation,  we  may  have  the  patient  raise  the  lip  by  the  use  of  the 
elevator  muscles  about  as  we  think  it  would  be  raised  in  smiling,  and 


III.   No.  24. Three  people  in  four,  when  smiling  unobserved,  raise  lips  to  level  of  neckS 

of  natural  centrals.     A  hearty  laugh  usually  elevates  the  lip  still    further. 


make  on  the  labial  surface  of  the  upper  trial  plate  a  horizontal  mark 
at  the  edge  of  the  lip,  as  in  Illustration  IvTo.  25.  The  lip  should  not 
be  raised  to  the  degree  of  a  hearty  laugh. 

The  line  thus  obtained  is  known  as  the  "  high  line,"  and  may  sug- 


31 

gest  to  us  the  proper  location  for  the  necks  of  the  artificial  centrals. 
The  distance  between  this  line -and  the  labio-incisal  angle  of  the  wax 
ridge  is  the  length  of  the  artificial  centrals,  save  for  the  collars  which 
are  embedded  in  the  vulcanite. 

Should  the  length  thus  indicated  be  obviously  too  great  or  too  short 
for  esthetic  results,  it  can  be  modified  at  will ;  but  experience  suggests 


III.   No.  25. — Marking  the  "  high  line." 


that  in  the  average  case  it  should  be  modified  only  after  careful  con- 
sideration. If  artificial  centrals  of  this  leugth  be  selected,  the  den- 
ture, when  exposed  in  smiling,  will  exhibit  a  maximum  of  porcelain 


32 

and  a  mininmni  of  vulcanite.  So  desirable  an  end  is  this  that  better 
results  are  obtained  by  selecting  upper  anteriors  as  nearly  of  this  length 
as  possible,  even  though  they  be  slightly  longer  than  the  contour  of  the 
face  might  indicate.  The  exercise  of  a  little  art  in  their  arrangement 
v\rill  partly  conceal  their  length ;  and  the  exhibition  of  vulcanite  should 
be  avoided  when  possible. 


III.    No.    26. — Marking  the   "  low   line." 


To  prevent  the  exhibition  of  the  vulcanite  of  the  lower  denture  when 
smiling  or  talking,  the  patient  should  depress  the  lower  lip  by  the  use 
of  the  depressor  muscles,  and  a  "  low  line  "  is  marked  on  the  lower 
bite,  as  in  Illustration  No.  26.     The  lower  lip  is  frequently  depressed 


33 

ill  laiigiiing,  or  by  movements  peculiar  to  the  person.  If  the  necks  of 
the  lower  centrals  be  located  at  the  low  line,  little  vulcanite  will  be  ex- 
hibited.    This  line  is  subject  to  change  at  will,  but  the  considerations 


III.  No.  27. — Marking  the  location  of  tlie  corners  of  the  orifice  on  the  upper  bite. 


which  govern  the  location  of  the  high  line  apply  here  with  equal  force. 

Having  determined  the  length  of  the  anteriors,  let  us  decide  on  the 

width  of  the  six  anteriors  taken  as  a  whole.     In  cases  where  the  orifice 

of  the  mouth  is  neither  noticeably  large  nor  small  as  proportioned  to 


34 

the  size  of  the  face,  pleasing  esthetic  results  may  be  realized  by  select- 
ing upper  anteriors  of  such  combined  width  as  will  bring  the  distal 
angles  of  the  cuspids  at  the  corners  of  the  orifice  of  the  mouth  when 
at  rest. 

To  register  on  the  bite  the  width  of  the  orifice,  place  an  instrument 
between  the  lips  at  the  median  line,  move  it  gently  to  one  corner  of 
the  orifice  and  make  a  vertical  mark  on  the  upper  bite,  and  then,  with- 


ILL.  No.  28. — Wax  bites  showing  marks  wliich  determine  the  sizes  of  teeth  required. 


out  disturbing  the  lips,  slide  it  between  them  to  the  other  corner  and 
make  a  similar  mark.  See  Illustration  'No.  2Y.  This  method  gives 
better  results  than  inserting  the  instrument  near  the  corners  of  the  ori- 
fice, which  tends  to  cause  the  patient  to  pull  the  corner  back  to  avoid 
the  instrument,  and  thus  enlarge  the  orifice. 

This  dimension  is  subject  to  the  same  modification  at  the  dentist's 


35 

discretion  as  the  length  of  the  anteriors.  In  some  cases  the  orifice  is 
large  in  proportion  to  the  face.  In  such  cases  the  anteriors  should  not 
be  as  wide  as  the  orifice.  In  some  cases  the  orifice  is  small;  the  ante- 
riors may  then  be  somewhat  wider.  In  cases  where  the  ridge  is  pointed 
at  the  median  line,  "  squirrel  mouthed,"  as  it  is  sometimes  called,  the 
anteriors  will  be  so  prominent  that  they  must  be  considerably  narrower 
than  the  distance  around  the  ridge  from  one  corner  of  the  orifice  to  the 
other.* 

After  the  trial  plates  have  been  removed  from  the  mouth,  they 
should  be  examined  and  the  approximation  of  the  ridges  in  the  molar 
region  noted.  A  point  should  be  selected  where  the  distal  surface  of 
the  upper  second  molar  is  to  come,  and  a  vertical  mark  made  opposite 
that  point  on  the  buccal  surface  of  the  wax  as  shown  in  Illustration  'No. 
28.  A  similar  mark  is  then  made  on  the  buccal  surface  of  the  opposite 
side. 

When  these  marks  have  been  made,  the  trial  plates  may  be  removed 
from  the  mouth,  the  marks  deepened,  and  a  little  black  wax,  such  as 
teeth  come  on,  may  be  run  into  each  mark.  This  will  locate  them  defi- 
nitely and  will  preserve  them  during  subsequent  handling. 

The  trial  plates  may  now  be  returned  to  the  mouth  and  a  final  de- 
cision reached  as  to  the  correctness  of  location  of  the  blackened  marks, 
especially  as  regards  the  width  of  the  six  anteriors.  If  anteriors  as 
wide  as  between  the  marks  would  be  noticeably  wide  for  that  face,  the 
marks  may  be  brought  together  until  the  width  would  appear  about 
normal.  A  second  guide  as  to  the  location  of  the  marks  will  be  found 
in  their  relations  to  the  cuspid  eminence.  If  the  marks  are  far  distal 
to  these  eminences  their  position  will  doubtless  require  modification. 

In  cases  where  no  other  guide  serves  to  indicate  the  proper  loca- 
tion of  these  marks,  they  may  well  be  placed  just  a  little  distally  of  a 
perpendicular  line  passing  beside  the  wing  of  the  nose.  Observation 
of  the  relations  between  the  wings  of  the  nose  and  the  natural  cuspids 
will  quickly  inform  a  dentist  as  to  this  relation. 

These  modifications  should  not  lead  anyone  to  underestimate  the 
value  of  these  marks.  Rightly  used,  they  will  be  found  of  the  greatest 
value  and  help. 

*  A  case  of  this  kind  was  recently  submitted  in  which  it  was  necessary  to  place 
the  distal  angles  of  the  first  bicuspids  at  the  corners  of  the  orifice. 


CHAPTEE   IV 

AN    IMPORTANT    DIMENSION    IN    ARTIFICIAL    TEETH 

How  shall  we  select  teeth  that  will  sit  in  right  relations  to  the  ridge 
without  the  need  of  grinding?  This  is  one  of  the  most  difficult  ques- 
tions the  plate  worker  has  to  settle.  The  necessity  for  accurate  selec- 
tion explains  why,  in  almost  every  dental  depot,  one  sees  dentists  try- 
ing teeth  on  models.  This  is  the  slowest,  most  inaccurate  and  most  ex- 
pensive form  of  tooth  selection,  but  is  made  necessary  by  the  fact  that 
most  dentists  do  not  know  how  to  select  a  mould  of  teeth  that  will  sit 
in  right  relations  to  the  ridge,  and  bring  the  cutting  edge  and  neck  in 
the  right  locations.  Since  it  is  with  artificial  teeth  we  are  to  work,  let 
us  study  them  for  a  little  and  learn  their  possibilities  that  we  may  se- 
lect them  intelligently. 

An  artificial  upper  central  presents  two  surfaces  which  are  im- 
portant for  widely  different  reasons.  Note  first  the  labial  surface.  It 
is  the  art  surface  of  the  tooth,  "  the  patient's  surface,"  we  might  call 
it.  Its  length  from  neck  to  cutting  edge,  its  width  from  side  to  side, 
its  outline  and  the  bulge  of  the  labial  surface  are  important  as  to 
whether  or  not  they  harmonize  with  the  patient's  face.  This  is  the 
surface  of  the  tooth  which  the  patient  sees ;  it  largely  determines  the 
appearance  of  the  finished  plate.  It  has  very  little  to  do  with  the  me- 
chanical side  of  plate  making  or  with  the  patient's  success  in  masticat- 
ing with  the  plate. 

But  the  other  surface  of  the  tooth,  the  overlooked,  neglected,  little- 
understood  lingual  surface,  is  especially  and  wholly  the  dentist's  sur- 
face. It  is  the  surface  whose  divisions  determine  the  mechanical  fit- 
ness of  any  tooth  for  the  case.     It  is  with  this  surface  that  dentists  have 


37 

unconsciously  wrestled  in  the  past.  This  surface,  properly  understood 
and  utilized,  will  do  much  to  make  the  mechanical  side  of  plate  work 
easy.  It  is  this  surface,  also,  which  largely  aifects  the  patient's  suc- 
cess in  mastication  and  clearness  of  enunciation. 

The  lingual  surface  of  an  anterior  tooth  shows  three  divisions.  The 
first  begins  at  the  cutting  edge  and  extends  cervically  to  a  pronounced 
ledge ;  this  portion  of  the  tooth  is  known  as  "  the  bite,"  because  it  is 
engaged  in  biting  food  by  contact  with  the  opposing  teeth.  The  next 
division  presents  a  flat  surface  from  which  the  pins  project.  It  is 
known  as  "  the  shut."  The  third  portion  extends  from  "  the  shut  "  to 
the  cervical  end  of  the  tooth;  it  is  known  as  "  the  ridgelap,"  because  it 
is  the  only  part  of  the  tooth  which  should  lap  the  ridge. 


COLLAR 


RIDGE 
?   LAP 


COMBINED 

BITE 

AND 

SHUT 


BITE 


III.  No.  29. — Diasrammatic  illustration  of  the  divisions  of  lingual 
surface  of  an  iipiier  central.  An  understanding  of  the  uses  of  these 
divisions  greatly  simplifies  artificial  tooth  selection. 


Dentists  have  been  accustomed  to  consider  these  divisions  of  the 
lingual  surface  separately.  They  have  attached  much  importance  to 
the  bite,  have  practically  ignored  the  shut,  and  have  selected  the  ridge- 
lap because  it  was  thick  or  thin  linguo-labially.  This  is  not  the  form 
of  consideration  which  brings  best  results. 

The  divisions  of  the  lingual  surface  of  an  artificial  tooth  fall  natur- 
ally into  two  groups,  according  to  their  functions.  The  bite  and  shut 
together  form  one  group  because  their  combined  length  should  carry 
the  incisal  edge  of  the  tooth  from  the  surface  of  the  gum  to  the  labio- 
incisal  angle  of  the  wax  ridge  of  the  trial  plate.     Note  that  it  is  not  the 


38 

bite  of  the  artificial  tooth  alone  which  carries  the  tooth  down ;  it  is  the 
combined  bite  and  shut.  Learning  first  to  group  these  two  divisions 
to  meet  this  requirement  will  greatly  aid  any  plate  worker  in  tooth  se- 
lection. The  remaining  division  of  the  lingual  surface,  the  ridgelap, 
stands  alone  as  to  function,  It  is  intended  to  lap  the  gum,  and  to  carry 
the  neck  of  the  tooth  up  to  the  high  line.  If  the  tooth  has  a  collar,  it  is 
supposed  to  be  covered  with  vulcanite,  as  a  lock  to  aid  in  supporting 
the  tooth  against  stress. 

The  manufacturer  supposes  that  the  dentist  will  select  a  mould  of 
teeth  in  which  only  the  ridgelap  will  rest  against  the  alveolar  ridge,  and 
the  bite  and  shut  will  come  below  it  in  an  upper,  or  above  it  in  a  lower. 
To  facilitate  such  selection  he  offers  teeth  of  the  same  length  and  width, 
with  the  divisions  of  the  lingual  surface  in  different  proportions.  For 
instance.  Illustration  'No.  30  shows  four  upper  centrals  which  are  of  pre- 
cisely the  same  length,*  but  in  which  the  divisions  of  the  lingual  sur- 


MouUl  4. 
Length  10  mm. 
Combined  bite  and 

shut  4J  mm; 
Bite  2  mm. 


Sloiild  11. 
Length   10  mm. 
Combined  bite  and 

shut  6  mm. 
Bite  2i  mm. 


Mould  13. 
Length   10  mm. 
Combined  bite  and 

shut  7  mm. 
Bite  3  mm. 


Mould  14. 
Length  10  mm 
Combined  bite  and 

shut   7i   mm. 
Bite  3i  mm. 


III.   No.  30. 

face  differ  greatly.  Not  only  are  these  centrals  of  the  same  length  and 
width,  but  the  six  anterior  teeth  in  each  of  these  moulds  are  of  the  same 
combined  width,  so  that,  but  for  differences  in  the  outlines  of  the  teeth, 
plates  made  from  these  four  moulds  appear  much  alike  when  seen  from 
the  labial  surface.  But  when  the  teeth  are  examined  from  the  lingual 
surfaces,  it  is  seen  that  hardly  any  two  of  them  are  mechanically  suited 
for  the  same  case. 

This  can  be  best  seen  by  studying  Illustration  ISTo.  31,  in  which, 
by  a  diagram,  each  mould  is  shown  in  section  on  a  case  for  which  it  is 
mechanically  adapted. 

Illustration  No.  31  supposes  that  each  of  these  moulds  has  been 
properly  selected  for  the  case.  By  properly  selected  is  meant  that  the 
cutting  edges  of  the  centrals  come  to  the  labio-incisal  angle  of  the  trial 


*  Twentieth  Century  Moulds  4,  11,  13,  14. 


30 


j)late,  the  necks  come  to  the  high  line,  and  the  bite  and  shut  sit  properly 
below  the  ridge. 

In  Illustration  JSTo.  31  A,  the  distance  between  the  ridge  and  the 

A  tooth  having  a  short  combined 


labio-incisal  angle  of  the  bite  is  short 


UABfO^NCISAL 
ANGLE 
OF   BITE 


Little     absorption.      Distance     from 

surface    of    ridge    to    labio-incisal 

.  angle  of  bite  is  short.     Requires 

tooth    with    short    combined    bite 

and  shut. 


Great    absorption.      Chance    to    use    tooth 
with  longer  bite  and  shut  than   in  31A. 


31C. 

Complete  absorption.     Distance   from   surface  of  ridge   to   labio-incisal   angle   of  bite 
permits  use  of  tooth  with  long  combined  bite  and  shut. 

III.  No.  31. 


hiie  and  shut  must  be  selected  if  it  is  to  set  properly  against  the  ridge. 
Many  dentists  have  given  much  attention  to  the  length  of  the  bite,  en- 
tirely overlooking  the  shut.  Here  is  where  they  fail.  It  is  not  the 
length  of  bite  alone  that  determines  the  mechanical  fitness  of  a  mould; 
it  is  the  length  of  the  combined  bite  and  shut.     If  these,  taken  together, 


40 

are  not  too  great,  the  lengtli  of  bite  may  be  nearly  as  desired.  J^ote 
that  the  mould  chosen  for  this  case  has  a  short  combined  bite  and  shut, 
4I/2  niillimeters,  but  the  total  length  of  the  tooth  is  such  as  to  meet 
the  artistic  requirements  of  the  case.  A  properly  divided  lingual  sur- 
face takes  care  at  once  of  the  tnechanical  fitness  of  the  mould. 

In  Illustration  ISTo.  SIB,  the  distance  from  the  surface  of  the  alveolar 
ridge  to  the  labio-incisal  angle  of  the  trial  plate  is  greater,  permitting 
the  use  of  a  tooth  with  a  longer  combined  bite  and  shut. 

In  Illustration  ISTo.  SIC,  absorption  of  the  alveolar  process  is  prac- 
tically complete.  The  distance  from  the  surface  of  the  alveolar  ridge 
to  the  labio-incisal  angle  of  the  trial  plate  is  great ;  and  a  tooth  having 
a  long  combined  bite  and  shut  should  be  used.  The  tooth  here  illus- 
trated has  a  moderately  long  bite,  but  the  bite  might  have  been  either 
shorter  or  longer,  so  long  as  the  combined  bite  and  shut  were  of  the 
proper  length. 


111.  No.  32. — Vertical  section  of  Mould  No.  1-1,  in  solid 
line,  contrasted  with  outline  of  Mould  No.  4,  in  dotted  line. 
Shows  the  disadvantages  of  using  moulds  with  short  com- 
bined bite  and  shut  when  a  long  combined  bite  and  shut  is 
indicated. 


It  is  evident  that  Mould  4,  shown  in  Illustration  'No.  SI  A,  would  go 
below  the  ridge  in  Illustration  ISTo.  SIC  without  grinding,  but  the  fol- 
lowing reasons  will  convince  the  careful  plate  worker  that  it  should 
not. 

First.  If  the  mould  in  Illustration  ISTo.  SI  A  be  set  below  the  ridge 
in  Illustration  No.  SIC,  it  will  come  where  the  dotted  line  in  Illustration 
No.  32  comes.  This  necessitates  much  thicker  rubber  over  the  alveolar 
ridge  and  makes  the  plate  more  heating  to  the  tissues,  and  more  likely 
to  vulcanize  porously. 

Second.  Mould  14  in  Illustration  ISTo.  SIC  has  a  long  bite.  It  simu- 
lates closely  the  natural  teeth  as  to  thinness  in  the  middle  and  incisal 
thirds.     It  makes  an  agreeable  place  for  the  tongue  in  articulation. 


41 

If  Mould  4  be  used,  it  extends  lingually  as  does  the  dotted  outline  in 
Illustration  'No.  32,  and  makes  an  awkward  place  for  the  patient's 
tongue  in  speech  and  mastication. 

Third.  The  bite  of  Mould  14  has  much  greater  cutting  power  than 
that  in  Mould  4.  It  cuts  through  food  where  Mould  4  crushes  through. 
Plates  made  with  anteriors  having  at  least  medium  long  bites  (a  me- 
dium bite  is  3  millimeters  long)  are  much  less  likely  to  be  thrown 
down  behind  in  the  act  of  biting.  It  is  therefore  advisable  to  use  teeth 
with  medium  long  bites  whenever  the  required  length  of  combined  bite 
and  shut  makes  it  possible,  save,  of  course,  in  end-to-end-bite  cases. 

Selecting  teeth  with  proper  bites  is  very  easily  done,  once  the  proper 
length  of  the  combined  bite  and  shut  has  been  determined.     It  is  neces- 


ILL.  No.  33. — Section  of  trial  plate  in  median  line  showing 
pin  as  llirnst  through  wax  ridge  in  proper  location  and 
direction. 


sary  only  to  decide  how  much  of  that  distance  shall  be  in  the  bite.  Sup- 
pose that  the  distance  from  the  surface  of  the  alveolar  ridge  to  the  labio- 
incisal  angle  of  the  trial  plate  is  7^2  millimeters,  the  combined  bite 
and  shut  of  the  required  artificial  central  should  not  be  greater  than  that 
distance.  We  may  now  decide  that  our  bite  shall  be  short  (2  to  3 
millimeters)  or  medium  (3  to  31/2  millimeters)  or  long  (over  31/2  mil- 
limeters). We  may  thus  decide,  before  we  look  at  a  tooth,  what  gen- 
eral form  it  shall  have.  The  method  of  applying  this  information, 
which  we  shall  soon  study,  is  very  simple. 

Having  learned  that  the  bite  and  shut  of  an  artificial  central  should 
sit  between  the  surface  of  the  ridge  and  the  labio-incisal  angle  of  the 


42 


bite,  it  remains  only  for  us  to  learn  how  great  that  distance  is  in  the 
case  for  which  we  are  selecting  teeth,  and  then  choose  a  mould  of  tooth 
having  a  combined  bite  and  shut  equal  to  the  distance. 

The  distance  between  the  surface  of  the  ridge  and  the  labio-incisal 
angle  of  the  bite  is  easily  learned.     Hold  the  trial  plate  so  that  the 


III.  No.  34. — Model  showing  thin  ridge.  In  such  a  case 
a  combined  bite  and  shut  not  greater  than  from  pin- 
hole down   is  indicated. 


III.  No.  35. — Section  of  model  showing  ridge  thick  linguo-labiall.y.  In 
such  a  case,  a  bite  and  shut  slightly  longer  than  from  pin-hole  down 
may  be  used. 

palatal  surface  can  be  seen  where  it  presses  against  the  alveolar  ridge 
in  the  median  line.  Thrust  a  pin  horizontally  backward  from  the  labial 
surface  of  the  trial  plate,  in  the  median  line,  at  such  level  that  it  pierces 
the  wax  just  level  with  the  surface  of  the  alveolar  ridge.  See  Illustra- 
tion :N'o.  33. 

The  pin-hole  locates  the  level  of  the  surface  of  the  alveolar  ridge  on 
the  labial  surface  of  the  wax.     The  distance  from  the  pin-hole  to  the 


43 

labio-incisal  angle  of  the  wax  is  the  space  available  for  the  bite  and  shut 
of  the  central. 

If  a  central  of  proper  length  and  having  a  combined  bite  and  shut 
nearly  equal  to  the  distance  from  the  pin-hole  to  the  labio-incisal  angle 
of  the  trial  plate,  be  properly  set  against  the  alveolar  ridge,  the  neck 
will  come  at  the  high  line  on  the  wax,  and  the  cutting  edge  at  the  labio- 
incisal  angle. 

There  is  one  exception  to  be  noted  in  obtaining  this  dimension,  and, 
properly  observed,  it  will  greatly  aid  us  in  selecting  teeth  for  close-bite 
cases,  because  it  affords  a  wider  range  of  moulds  to  select  from.  This 
exception  obtains  only  in  cases  where  the  ridge  is  thick  linguo-labially. 
It  can  be  best  understood  by  repeating  an  illustration  and  studying  it 
from  a  new  viewpoint. 

In  Illustration  jSTo.  34  the  ridge  is  thin  linguo-labially.  The  pins 
of  the  artificial  tooth  will  extend  across  it ;  they  will  come  on  the  lowest 
part  of  its  surface.  Therefore,  in  this  case,  all  that  has  been  said  above 
about  the  combined  bite  and  shut  not  being  greater  than  from  the  lowest 
point  of  the  ridge  to  the  labio-incisal  angle  of  the  trial  plate  applies  ex- 
actly. But  in  Illustration  ISTo.  35  is  shown  a  section  of  a  very  different 
type  of  alveolar  ridge.  This  ridge  is  thick  lingiio-labially.  When  the 
teeth  are  set  as  they  would  be  in  most  cases  (the  labial  surface  of  the 
built-up  wax  ridge  will  show  how  they  are  to  set  for  any  given  case),  the 
teeth  cannot  reach  far  enough  under  the  ridge  to  bring  the  bite  and  shut 
below  the  loivest  point,  but  they  will  come  anterior  to  and  a  little  above 
that  point.  Therefore,  when  the  ridge  is  thick  linguo-labially  and  the 
teeth  are  to  set  slightly  forward  of  the  ridge  instead  of  against  it,  the 
combined  bite  and  shut  may  be  at  least  a  millimeter  greater  than  the 
distance  between  the  pin-hole  and  the  labio-incisal  angle.  And  the  teeth 
will  still  go  to  place  without  grinding. 


CHAPTEE    V 

GETTING   THE   EXACT   DIMENSIONS   OF   THE   BEQUIEED   AETIFICIAE   TEETH 

The  onlj  appliance  needed  for  getting  the  dimensions  of  the  re- 
quired teeth  is  a  flexible  millimeter  measure.  On  a  foot-rule  there  is 
usually  no  division  less  than  1-16  of  an  inch,  and  this  is  too  large  a 
dimension  for  measuring  teeth.  After  long  study  the  writer  adopted  a 
millimeter  as  the  most  convenient  unit  of  measurement.  The  milli- 
meter measure  should  be  flexible,  so  that  it  may  be  bent  about  the  bite. 
There  is  outside  evidence  that  the  use  of  the  millimeter  v^as  wise,  be- 
cause, soon  after  the  writer  brought  out  the  method  here  outlined,  he 
received  a  letter  from  a  Southern  dentist  saying  that  he  had  devised  a 
similar  method  of  measuring  teeth  several  years  before.  He  had  no 
doubt  this  method  was  based  on  his;  in  this  he  was  in  error,  since  the 
writer  knew  of  no  similar  method. 

With  the  millimeter  measure,  get  the  distances  in  millimeters  be- 
tween the  marks  on  the  trial  plate ;  turn  to  tables  where  artificial  teeth 
are  described  in  millimeters,  and  select  the  mould  of  teeth  most  nearly 
conforming  to  the  requirements.  ISTote  the  number  of  the  mould  and 
order  by  that  number.  That  is  all  there  is  to  this  method.  It  saves 
time  and  errors  every  time  it  is  intelligently  used. 

The  first  step  is  to  get  the  length  of  upper  centrals.  To  do  this, 
measure  between  the  high  line  and  the  labio-incisal  angle  of  the  upper 
trial  plate.  This  does  not  give  the  full  length  of  central;  it  gives  the 
length  of  the  labial  surface,  the  part  that  is  to  show ;  above  this  part  of 
the  tooth  must  be  a  collar  that  extends  into  the  vulcanite,  when  there 
are  to  be  rubber  gums  in  front.  Some  moulds  of  artificial  teeth  do  not 
have  collars,  but  the  neck  of  the  tooth  itself  then  extends  into  the  rubber. 


45 

The  artificial  central  should  be  at  least  a  millimeter  longer  than  the 
distance  from  the  high  line  to  the  labio-incisal  angle.  On  the  trial  plate 
here  measured,  the  distance  from  the  high  line  to  the  labio-incisal  angle 
is  9%  millimeters;  adding  1  millimeter  for  the  part  of  the  tooth  to 
enter  the  rubber,  indicates  a  length  of  10^  millimeters  for  the  required 
central. 


III.   No.  36. 


A  millimeter  is  equal,  for  all  practical  purposes,  to  1-25  of  an  inch. 
It  is  evident,  therefore,  that  a  variation  of  I/2  a  millimeter  either  way  in 
the  length  of  the  central  will  make  no  serious  difference.  It  may,  there- 
fore, be  decided  that  the  central  should  be  from  101/4  to  11  millimeters 
long.  This  gives  a  wider  range  of  moulds  from  which  to  select  to  meet 
the  other  requirements.  This  dimension,  "  Length  of  central,  lO^/o 
mm.,"  should  be  noted. 

The  distance  between  the  pin-hole  and  the  labio-incisal  angle  of  the 
upper  trial  plate  indicates  the  proper  length  of  the  combined  bite  and 
shut  of  the  artificial  central.  If  the  ridge  is  thin  linguo-labially  and  the 
teeth  are  to  set  close  to  it,  this  dimension  should  not  be  increased.    But 


46 

if  the  teeth  are  to  set  well  away  from  the  ridge,  or  the  ridge  is  thick 
linguo-labially,  this  dimension  may  be  increased  a  millimeter,  as  has 
been  explained.  The  distance  from  the  pin-hole  to  the  labio-incisal  angle 
of  this  trial  plate  is  T^/^  millimeters.  The  combined  bite  and  shut  of 
the  central  then  should  not  be  greater  than  7i/o  millimeters.  If  the  bite 
and  shut  are  correct  in  the  central,  they  will  probably  be  so  in  the  other 
teeth  of  the  set. 

Get  next  the  width  of  the  six  anteriors  taken  together.  This  is  more 
important,  for  the  present,  than  the  width  of  the  central  alone,  since  the 
anteriors  as  a  whole  strike  the  eye  first  when  the  plate  is  seen.    Measure 


III.    No.    37. — Measuring  bite  horizontally   to  get   combined   width   of   six    anteriors 
and  full  set   of   14. 


between  the  vertical  marks  made  at  the  corners  of  the  mouth.  This  is 
the  distance  from  the  distal  angle  of  one  upper  cuspid  to  the  distal  angle 
of  the  other  ivlien  the  teeth  are  set  up.  This  is  quite  different  from  the 
distance  between  these  angles  as  these  teeth  lie  flat  on  the  wax  on  which 
they  are  sold.  This  point  should  be  borne  in  mind.  The  third  require- 
ment then  is  "  Combined  width  six  anteriors,  43  millimeters." 

To  get  the  width  of  the  full  set  of  14  teeth  when  set  up,  measure 
between  the  marks  made  to  locate  the  distal  side  of  the  upper  molars. 
Do  this  by  bending  the  rule  close  about  the  outside  of  the  upper  trial 


47 

plate  at  the  iiicisal  angle.  Suppose  this  distance  to  be  101  millimeters. 
As  in  the  case  of  the  anteriors,  this  dimension  is  quite  different  from  the 
width  of  the  teeth  as  they  lie  flat  on  the  wax  on  which  they  come  from 
the  dealer. 

When  this  dimension  has  been  noted  the  requirements  are  as  follows : 

Length  upper  central,  10^  mm. 

Combined  bite  and  shut,  not  over  71^  mm. 

Combined  width  6  anteriors,  43  mm. 

Combined  width  full  14,  101  mm. 
These  dimensions  are  much  more  valuable  for  selection  than  mere 
sight  of  the  teeth  could  be.  It  is  well  known  that  the  sight  of  many 
teeth  confuses  the  one  who  is  selecting.  The  eye  does  not  perceive 
actual  dimensions — it  sees  only  proportions.  A  certain  mould  may 
"  look  about  right,"  when  really  not  a  single  dimension  fits  the  require- 
ments. Having  in  hand  the  actual  dimensions  of  the  required  teeth 
will  help  us  wonderfully. 

The  dimensions  of  the  lower  teeth  may  be  easily  gotten  if  desired. 
But  the  anatomical  moulds  are  furnished  in  sets  of  .28,  that  is,  full 
uppers  and  lowers.  The  lower  anteriors  have  been  carefully  selected  to 
harmonize  in  character  with  the  uppers  and  to  be  of  proper  widths  for 
articulation.  It  will  generally  be  found  satisfactory  to  select  the  uppers 
to  meet  the  requirements  and  to  use  the  lowers  carded  with  them.  If, 
however,  it  is  desired  to  get  the  dimensions  of  the  lowers,  proceed  as 
follows.  To  get  the  length  of  central,  measure  from  the  low  line  to  the 
rest  line.  The  lower  anteriors  underbite  the  upper  anteriors  and  should 
extend  as  high  as  the  rest  line.  Add  1  millimeter  for  collar,  making  the 
length  of  the  desired  central  11  millimeters.  A  pin  is  thrust  through 
the  lower  trial  plate  to  locate  the  surface  of  the  alveolar  ridge  in  the 
same  way  that  the  surface  of  the  upper  alveolar  ridge  was  located. 
Measure  for  the  combined  bite  and  shut  as  on  the  uppers.  The  distance 
in  this  case  is  8  millimeters.  The  requirements  for  the  lower  centra 
are  as  follows : 

Length,  11  mm. 

Combined  bite  and  shut,  not  over  8  mm. 
If  lowers  other  than  those  carded  vnth  the  uppers  are  desired  to 
articulate  with  uppers,  being  made  at  the  same  time,  or  if  the  lowers  are 
selected  for  a  lower  plate  which  is  being  made  alone,  the  width  of  the  6 
anteriors  and  the  full  14  must  be  gotten  also. 

Having  the  dimensions  of  the  required  teeth,  either  of  three  methods 
of  selection  may  be  followed.     The  first  is  to  measure  artificial  teeth  a 


48 

thej  lie  on  the  wax.  The  only  dimensions  which  come  right  by  this 
method  are  the  length  of  the  centrals  and  the  combined  bite  and  shut. 
The  widths  of  the  anteriors  and  of  the  fnll  set  will  not  be  riffht.  The 
second  course  is  to  measure  pictures  of  artificial  teeth  as  they  appear 
in  catalogues.  This  is  subject  to  the  same  errors  as  the  first  course, 
with  a  few  additional  errors  due  to  engravings  not  always  being  exact. 
The  only  other  course  is  to  have  access  to  tables  where  the  dimensions 
of  artificial  teeth  in  millimeters  are  given  to  meet  such  requirements. 
Only  one  tooth  manufacturer  has  so  far  published  such  tables  of  moulds, 
and  from  those  tables  selection  will  be  made.*  The  dimensions  here 
given  are  not  exact,  because  teeth  vary  a  trifle  in  shrinkage  during  bak- 
ing, but  they  are  very  close.  Thus,  the  combined  width  of  six  anteriors 
may  vary  a  millimeter  or  so  either  way  from  the  dimensions  given  here, 
but  even  with  this  variation  the  accuracy  is  greater  than  is  obtainable 
by  any  other  method. 

Great  care  was  taken  to  get  these  dimensions  correct.  After  re- 
peated measurings  of  the  teeth,  a  Bonwill  circle  was  cut  in  cardboard 
for  each  mould  and  the  teeth  set  to  it  on  wax.  They  were  then  measured, 
and  the  dimensions  here  given  were  verified.  There  may  still  be  slight 
errors  in  the  dimensions,  but  almost  endless  pains  were  taken  to  have 
them  correct. 

The  requirements  for  upper  teeth  are  as  follows : 
Length,  10^  to  11  mm. 
Combined  bite  and  shut,  not  over  7^/^  mm.,  but  as  near  it  as 

possible. 
Combined  width  6  anteriors,  43  mm. 
Width  full  set  of  14,  101  mm. 

Page  ^o.  49  of  this  book  shows  a  portion  of  the  table  giving  the 
dimensions  of  the  plain  vulcanite  teeth,  uppers  arranged  in  order  by 
size.  The  first  column  gives  the  mould  numbers;  each  mould  is  de- 
scribed by  the  figures  in  the  remainder  of  its  line.  This  column  is  im- 
portant, because  when  teeth  of  proper  size  are  found  they  should  be 
ordered  by  the  mould  number. 

The  next  column  gives  the  length  of  the  central  in  the  mould.  This 
is  the  column  used  first,  since  the  length  of  central  is  the  most  con- 
venient dimension  with  which  to  begin. 

The  third  column  gives  the  combined  width  of  the  six  anteriors 
when  set  uj).     This  dimension  corresponds  to  the  distance  between  the 

*  The  Dentists '  Supply  Company  in  the  Twentieth  Century  Mould  Book.  The 
writer  spent  nearly  a  year  working  out  the  methods  here  described  and  their  appli- 
cation in  the  forms  of  tables.  The  publishers  of  this  book  spent  $15,000.00  in  pre- 
senting this  information,  as  applied  to  their  products,  to  the  profession. 


49 

marks  at  the  corners  of  the  mouth.     The  nse  of  this  column  next,  per- 
mits much  more  rapid  selection  than  any  consideration  of  the  width  of 


MEDIUM  LONG  MOULDS, 

(ALL  DIMENSIONS  ARE  IN  MILLIMETERS.) 


Approx. 
width  6 
anteriors 
set  on 
BoQwUl 
Circle 


set  on 
BonwiU 
Circle 


Combined 

Bite  and  Shut 

of  central 


Articulates  with  lower  moulds 


MEDIUM  LOMG  AND  NARROW. 


MEDIUM  LONG  AND  MEDIUM  WIDE. 


MEDIUM  LONG  AND  WIDE. 


Cut 

and 
descrip- 
tion  OK 

page 


4' 

10 

-43 

103 

4K 

2 

7 

3-21-9-65 

29 

11 

10 

43 

102 

5K 

2X 

7 

7-2-10 

30 

14 

10 

43 

105 

7'A 

3K 

7 

al4-2-3-8-70 

30 

16 

10 

42 

99 

4K 

2 

7 

-24-7-27 

30 

31 

10 

42 

103 

5 

2 

6H 

7-2-70 

30 

41 

10 

43 

103 

5K 

2'A 

7 

7-8-2-10 

31 

89 

10 

42 

98 

7 

3K 

7 

8-2-3-10 

31 

67 

10 

40 

100 

6K 

2'A 

6?^ 

67-7-2 

31 

37 

lOK 

43 

104 

7 

3 

7 

a37-3-2-8-70 

31 

19 

W'/i 

43 

104 

6 

3 

7 

al9-7-24-2-8 

32 

30 

lOK 

42 

100 

7 

3 

7 

a30-3-2-7-17 

32 

90 

10>^ 

42 

100 

7'A 

4 

7 

90 

32 

27 

lOM 

40 

101 

S'A 

4 

6K 

2S-7 

32 

51 

11 

42 

102 

7K 

3 

7 

51-11-3 

33 

91 

11 

42 

99 

5K 

2 

6X 

91-2-7 

33  ^ 

13 

10 

43 

107 

7 

3 

7y 

65-3-21-5 

33 

20 

10 

44 

106      , 

6K 

3 

7y 

53-1-5-24 

34 

88 

10 

45 

108 

6K 

sy 

7y 

9-3-2-24-70 

34 

5 

10 

44 

105 

6M 

3- 

7y 

a5-2-«-21-53 

34 

6 

10 

45 

106 

5K 

2K 

7y 

a8r-3-21-53-9-8 

34 

72 

10 

47 

115 

QA 

3 

7% 

72-73-43 

35 

23 

10 

45 

109 

6 

2y 

7y 

40-5-65 

35 

7 

lOK 

45 

110 

7A 

4 

7y 

1-5-92 

35 

24 

lOK 

43 

108 

7A 

,3K 

7 

1 

35 

2 

lOK 

45 

104 

ey. 

3K 

7y 

3-8-2-10, 

35 

35 

lOK 

45 

106 

7y 

4 

7M 

a35-65^5 

36 

79 

10^ 

45 

108 

7% 

4 

7y 

79-5-6 

36 

39 

loy. 

43 

103 

7 

2y 

7y 

8-2-10-7 

36 

25 

^0% 

44 

107 

6K 

3 

7y 

5-3-65-16-53 

36 

92 

lOK 

45 

110 

7y 

4 

7y 

92-5-103 

37 

9 

10% 

45 

107 

7A 

4 

7% 

6-5-40-79-92 

37 

40 

11 

44 

105 

7% 

4y 

7 

8-2-3-7 

37 

28 

11 

45 

106 

5A 

2 

7K 

65-16-3-11 

37 

29 

11 

45( 

109 

7 

sy. 

7y 

1-16-5-103 

38 

63 

11 

44 

103 

5y 

2y 

7y 

S-7-10 

38 

65 

11 

45 

106 

6K 

3 

ly 

65-3-11-21 

38 

12 

11 

46 

106 

6K 

3K 

7y 

5-6-16-79 

38 

46 

ny. 

44 

105 

9K 

sy 

7y 

3-5-11-16 

39 

66 

ny 

45 

114 

8K 

3y 

7X 

66 

39 

103 

ny 

47 

114 

9 

4 

7y 

103-92 

39 

75 

47 


9K 
lOK 


50 
46 


116 
HO 


6K 
6 


3 


9K 
8 


75-69-19 
6-5H28-79-40 


39 
4D 


Portion  of  table  showing  measurements  of  plain  vulcanite  teeth. 


the  central  at  this  time.     There  are  usually  several  moulds  having  an- 
teriors of  approximately  the  desired  width. 

The  fourth  column  gives  the  width  of  the  full  set  of  14  teeth,  set  up. 


50 

This  dimension  corresponds  to  the  distance  between  the  marks  for  the 
distal  sides  of  the  second  molars. 

The  next  column  gives  the  combined  bite  and  shut  of  the  central  in- 
cisor. This  measurement  corresponds  to  the  distance  between  the  pin- 
hole and  the  labio-incisal  angle  of  the  upper  trial  plate.  Taken  with  the 
three  columns  just  preceding,  it  completes  the  most  important  dimen- 
sions of  the  teeth. 

When  the  combined  bite  and  shut  have  been  found,  the  length  of 
bite  and  the  width  of  the  central  will  help  in  making  the  selection  more 
exact.    These  dimensions  are  given  in  the  next  two  columns. 


III.  No.  38. — Patient  for  whom  uppers  and  lowers  were  selected  in 
5  minutes  after  bites  were  marlied.  The  upper  anteriors  just 
cover  the  area  of  plate  exposed  in  smiling.  The  lowers  for  the 
same  case  are  shown  in  the  next  illustration. 


As  evidences  of  the  results  easily  attainable  by  this  method  of  selec- 
tion, a  few  photographs  of  patients  are  here  exhibited,  with  the  teeth 
in  position. 


51 

The  usefulness  of  the  wide  column  headed  "Articulates  with  Lower 
Moulds  "  has  been  greatly  lessened  by  improvements  in  the  moulds  and 
carding  of  artificial  teeth  since  this  book  was  published.  It  will  gen- 
erally be  found  most  advisable  to  use  the  teeth  as  they  now  come  carded 
and  the  figures  in  this  column  may  be  disregarded. 

The  last  column  gives  the  page  of  the  book  on  which  each  mould  in 
the  table  is  illustrated  and  described. 


III.  No.  39. — Lowers  in  the  case  shown  on  the  preceding  page. 
When  the  lower  lip  is  depressed,  the  festoons  about  the  anteriors 
are  barel.v  exposed.  The  only  rubber  shown  is  that  in  the  inter- 
proximal   spaces. 


All  the  moulds  in  the  table  are  divided  into  three  groups :  "  ITar- 
row,"  '•  Medium  Wide  "  and  "  Wide."  This  is  to  further  facilitate 
selection.  Only  two  divisions  of  the  table  of  "  Medium  Long  Moulds  " 
are  reproduced  here  because  of  lack  of  space. 

JSTow  that  we  understand  the  table,  let  us  select  a  mould  to  meet  the 
requirements.  A  central  IQi/o  to  11  millimeters  long  is  required.  In 
the  "  Medium  Long  and  I^arrow  "  section  of  the  table  seven  moulds  of 
the  desired  length  are  listed.  Mould  37,  the  first  of  these,  is  of  the  cor- 
rect width  in  the  anteriors,  but  too  wide  in  the  full  14.  Mould  19  is 
too  wide  in  the  anteriors.     Mould  30   is  of  the  desired  dimensions 


52 

throughout;  the  same  is  true  of  Mould  90.  Mould  27  has  the  proper 
length  of  central,  but  is  narrow  in  the  anteriors'  and  too  long  in  the  bite 
and  shut.  If  the  central  from  Mould  51  is  properly  set  against  the 
ridge,  the  cutting  edge  will  come  at  the  labio-incisal  angle  of  the  trial 
plate,  the  neck  at  the  high  line,  the  distal  angles  of  the  cuspids  at  the 
corners  of  the  mouth  and  the  distal  sides  of  the  second  molars  at  the 
marks  made  for  them. 

Mould  51  is  correct  in  all  its  dimensions.  This  gives  three  moulds 
to  choose  from,  30,  90  and  51.  The  choice  among  these  moulds  must 
be  decided  by  their  artistic  suitability  for  the  case.  By  turning  to  pages 
32  and  33  of  the  book  here  in  use,*  the  illustrations  show  the  outlines 
of  the  anteriors  to  be  as  reproduced  here. 


III.  No.  40. — The  character  of  these  moulds  may  be  determined  from  this  illustration. 

By  referring  to  Illustration  N^o.  21,  page  25  of  this  book,  the  outline 
of  the  patient's  face  may  be  seen  in  part.  But  it  is  there  shown  at  a 
little  more  than  full  face  and  seems  rounder  than  it  really  is. 

While  the  outline  of  Mould  30  would  be  fairly  satisfactory  for  this 
face,  the  writer  thinks  it  not  equal  to  one  of  the  others,  partly  on  account 
of  the  long  narrow  lateral. 

The  outline  of  Mould  90  is  not  suitable.    The  central  of  this  mould 


The   Twentieth   Century   Mould   Book. 


53 

shows  much  flatter  curves  in  the  middle  and  cervical  thirds  than  are 
manifested  in  the  lower  part  of  this  patient's  face. 

Mould  51  is  more  pleasing  than  either  of  the  other  two,  partly  be- 
cause the  outline  harmonizes  with  the  outline  of  the  patient's  face,  and 
partly  because  it  is  a  lap-lateral  mould.  By  "  lap-lateral  "  is  meant  that 
the  laterals  are  so  made  that  they  may  be  set  to  lap  the  centrals  if  nec- 
essary. 


III.  No.  41. — The  anteriors,  both  uppers  and  lowers,  are  of  correct 
lengths  to  prevent  pink  rubber  gums  showing  in  smiling.  It  is 
believed  that  the  teeth  harmonize  with  the  face  in  length, 
width  and  outline.  Time  required  to  select  uppers  and  lowers 
after   bites  were  marked,   5   minutes. 


The  irregularities  which  may  thus  be  produced  very  greatly  increase 
the  artistic  value  of  the  denture. 

Having  determined  what  mould  is  desirable  for  the  case,  it  should  be 
ordered  by  mould  number.     The  order  for  this  case  reads : 

Send  me  1  x  28 teeth. 

Upper  Mould  51,  with  appropriate  lower,  shade  10. 
The  selection  of  artificial  teeth  should  not  be  left  to  the  tooth  clerks. 


54 

That  is  a  manifest  absurdity.  The  tooth  clerk  never  sees  the  patient. 
He  is  usually  furnished  such  meagre  information  as  would  preclude 
satisfactory  selection  by  any  one;  and  he  is  not  expected  to  be  a  prac- 
tical plate  worker.  Tooth  selection  has  been  left  to  him  because  den- 
tists in  general  have  not  been  sufficiently  well  informed  to  make  their 
own  selections.     The  dentist  who  knows  every  detail  of  the  case  is  evi- 


III.  No.  42. — Artificial  uppers  selected  to  articulate  with  natural 
lowers.  It  is  believed  these  teeth  are  harmonious  in  every 
particular  with  the  face.  The  very  light  color  which  they 
exhibit  is  merely   a   printing  effect. 


dently  the  one  who  should  master  tooth  selection  and  should  order  hy 
mould  number,  leaving  to  the  tooth  clerk  merely  the  duty  of  properly 
filling  the  order. 

Some  dentists  have  adopted  this  method  in  part,  and  in  ordering 
teeth  specify  the  length  and  width  in  millimeters.  It  is  believed  that  a 
little  more  study  and  courage  would  enable  them  to  carry  their  work 
one  step  farther  and  select  the  mould  themselves.  This  would  be  much 
more  satisfactory  in  the  end. 


55 

It  may  be  well  to  ask  what  has  been  learned  which  shall  justify  the 
use  of  this  method  of  selection.  It  seems  to  the  writer  that  these  results 
can  be  summed  up  as  follows : 

First.  Our  own  knowledge  of  artificial  teeth  has  been  greatly  in- 
creased. Since  the  writer  began  the  studies  which  led  to  these  articles, 
he  has  learned  things  about  artificial  teeth  which  nobody  ever  took  the 
pains  to  teach  him,  and  which  are  of  great  practical  value.  By  means 
of  these  studies  we  have  learned  to  know  what  we  want  in  artificial 
teeth ;  this  has  not  always  been  the  case  in  the  past. 

Second.  We  are  now  able  to  specify  to  the  tooth  clerk  just  what 
moulds  we  want — a  thing  impossible  before.  We  may  send  or  phone 
or  write  with  a  certainty  of  getting  what  we  require. 

Third. — We  need  not  send  models  to  the  dealers.  Sending  the  mould 
number  answers  every  purpose.  It  also  greatly  facilitates  orders  being- 
filled  with  rapidity  and  accuracy  at  the  depot. 

Fourth.  We  economize  time.  It  takes  a  little  time  to  learn  to  order 
moulds  by  this  method,  just  as  it  takes  a  little  time  to  learn  to  do  any- 
thing else ;  but  the  writer  has  met  many  dentists  who  are  pleased  with 
this  method,  and  their  reports  are  that  after  the  first  two  or  three  cases 
they  were  enabled  to  choose  moulds  to  their  complete  satisfaction  in  a 
very  few  moments. 

Fifth.  There  is  no  necessity  to  grind  the  teeth,  provided  we  have 
used  care  in  selecting. 

Sixth.  We  get  better  artistic  and  mechanical  results  with  very  much 
less  labor. 

Seventh.  Anatomical  articulation  of  artificial  teeth  will  soon  be  the 
standard  method.  It  is  now  required  in  the  colleges,  and  by  law  in 
some  states.  We  older  dentists  must  learn  it  or  we  shall  soon  be  out- 
classed. This  form  of  articulation  will  be  greatly  facilitated  if  we  know 
first  how  to  properly  select  the  teeth  for  any  given  case. 


CHAPTER   VI 

MOUNTING    THE    TRIAL     PLATES     AND     MODEL3     ON    THE     ARTICULATOR 

THE   USE   OF   THE   FACE    BOW 

As  one  progresses  in  the  practice  of  anatomical  articulation  he  re- 
alizes more  and  more  the  necessity  of  accuracy  at  each  step.  For  one 
step  falsely  made  may  defeat  the  greatest  care  at  all  other  points. 

111.  ISTo.  43  shows  by  means  of  a  cardboard  model  the  result  that  fol- 
lows when  the  models  are  not  attached  at  their  proper  distance  from  the 
condyles  and  the  height  of  the  bite  must  be  changed.  The  models  in  A, 
in  111.  'No.  43  have  been  attached  too  far  forward,  and  the  teeth  have  been 
articulated  accordingly.  When  these  are  tried  in  the  mouth,  only  the 
molars  will  come  into  contact,  the  incisors  failing  to  meet,  while  on  the 
contrary,  when  the  models  have  been  attached  too  far  back,  only  the 
incisors  will  come  into  contact,  and  the  molars  will  fail  to  meet. 

Models  can  be  accurately  mounted  on  the  articulator  by  only  one 
means;  that  is  the  use  of  the  face  bow.  When  these  articles  were 
written,  there  was  but  one  face  bow  generally  known  in  this  country, 
that  made  by  Dr.  George  B.  Snow.  Since  that  time  the  excellent  articu- 
lator of  Dr.  Gysi  has  been  introduced  to  American  dentists.  It  carries 
the  face  bow  idea  perhaps  even  farther  than  Dr.  Snow  applied  it  in 
ordinary  work.  The  Gysi  articluator  requires  more  time  and  atten- 
tion in  the  early  stages  of  denture  making  than  the  one  described  in 
the  following  pages.  The  writer's  opinion  is,  after  very  limited  ex- 
perience with  it,  that  during  the  latter  stages  it  saves  as  much  time  as 
it  required  extra  in  the  earlier  stages,  and  that  it  will  make  possible 
results  never  before  within  our  reach.  The  writer  understands  that  one 
of  America's  leading  plate  workers  is  about  to  produce  a  new  articulator, 
and  this  feature  will  doubtless  be  embodied  therein.  While  the  distance 
from  the  condyle  to  the  incisal  edges  of  the  lower  centrals  at  the  median 
line  may  average  four  inches,  it  varies  in  practice  from  3%  to  4% 
inches.  Without  entering  into  the  mathematics  of  the  effects  of  such 
varying  distances,  it  may  be  said  that  it  is  well  worth  the  necessary 
trouble  to  mount  the  models  on  the  articulator  in  such  a  way  as  to  re- 
produce the  incisor-to-condyle  distance  peculiar  to  the  case  in  hand. 


57 

Probably  more  dentures  exhibit  faulty  articulation  in  the  mouth  be- 
cause of  the  models  having  been  incorrectly  set  on  the  articulator  than 
from  any  other  cause;  for  dentures  set  to  articulate  at  one  distance 
from  the  joint  will  not  articulate  at  a  greater  or  lesser  distance  when 
the  height  of  the  bite  *  is  changed. 

There  is  scarcely  a  probability  of  the  models  being  placed  on  the 
articulator  by  chance  so  as  to  reproduce  the  condyle-to-incisor  distance 
peculiar  to  that  patient.  Unless  that  distance  is  correctly  reproduced, 
the  dentures  articulated  on  the  models  thus  placed  are  less  likely  to  ar- 
ticulate well  in  the  mouth. 


III.    No.   43. — Upper  half  models   attached  to  articulator  with   too  great  incisor-to-condyle  distance 

and  teeth   articulated. 
Lower  half.      The  dentures,    articulated   as   above,    are  put   into   the  mouth.    Only   the    molars   strike. 

Such    "  guesswork  "    attachment    of    models    to    articulators    accounts    for    many    articulation 

failures,  f 

Many  articulation  failures  can  be  avoided  by  accuracy  at  this  point. 
This  applies  as  strongly  to  dentures  articulated  in  the  common  way  as 
to  those  articulated  anatomically. 

With  both  trial  plates  in  the  mouth,  the  closure  of  the  jaws  in  proper 
relations  is  secured  by  any  method  satisfactory  to  the  operator. 

While  the  jaws  are  held  in  these  relations,  continuous  vertical  marks 
should  be  made  across  the  buccal  surfaces  of  both  trial  plates  so  that 
they  may  be  replaced  in  proper  relations  to  each  other  after  removing 

*  By  bite  is  here  meant  the  separation  between  the  upper  and  lower  alveolar 
ridges  in  position  of  normal  closure. 

■j-  Published  by  the  courtesy  of  Dr.  George  B.  Snow  and  reproduced  from  The 
Dental  Cosmos  for  February,  1910. 


58 

from  the  mouth.  They  are  then  removed,  placed  in  proper  relations  to 
each  other  and  sealed  together  with  a  hot  spatula. 

Distortion  of  the  trial  plates  will  be  much  less  likely  to  occur  in 
handling,  if  they  are  placed  on  their  respective  models  immediately 
after  removing  from  the  mouth  and  handled  thus. 

One  portion  of  the  Snow  Face  Bow  consists  of  a  straight  cylindrical 
rod  with  a  flat  curved  piece  across  the  end;*  this  entire  piece  is  known 


III.  Wo.  44. — Model.s  of  two  natural  dentures  showing  wide  variation 
in  the  incisor-to-contlyle  distance.  In  the  upper  model  this  distance 
is  3f  inches.  In  the  lower,  it  is  4i  inches.  For  the  significance 
of   this   variation,    see    Illustration    No.    43. 


as  "  the  mouth  piece."  The  fiat  curved  cross  part  is  now  heated  to  a 
temperature  which  really  softens  wax,  and  is  inserted  deeply  into  the 
labial  surface  of  the  upper  trial  plate  as  nearly  like  Illustration  'No.  4:5 
as  possible. 

*  When  this  article  was  written,  the  form  of  the  mouth  piece  in  common  use 
for  this  work  was  as  described  here.  Since  then  another  form  has  been  introduced; 
literature  making  plain  its  use  accompanies  each  face  bow. 


59 

It  will  be  noticed  that  the  stem  of  the  mouth  piece*  is  parallel  with 
the  occlusal  plane  of  the  trial  plates.  It  also  projects  forward  as  a  con- 
tinuation of  the  median  line  of  the  body.  Care  must  be  exercised  to  see 
that  this  mouth  piece  is  firmly  seated,  so  that  the  trial  plates  may  be 
handled  by  it  without  loosening.  In  cases  where  it  is  difiicult  to  seat 
it  firmly  in  the  manner  shown  here,  it  should  be  seated  as  well  as  may 
be  and  additional  wax  flowed  about  it. 


III..   No.  45 


-Trimmed  bites  held  on  models  and  mouth  piece  of  face  bow  flvmly  seated  parallel  with 
occlusal  plane  of  bites. 


The  trial  plates,  still  fastened  together  and  with  the  mouth  piece 
attached,  are  laid  aside  while  preparations  are  made  for  using  the  rest 
of  the  face  bow.  Place  the  finger  on  the  side  of  the  face  and  locate  the 
head  of  each  condyle.  Perhaps  this  can  be  best  done  by  having  the 
patient  depress  the  mandible  so  that  the  finger  sinks  into  the  depression 

*  Held  in  the  right  hand. 


60 

left  behind  the  condyle  as  it  moves  forward.  By  having  the  jaw  slowly 
closed,  the  return  of  the  mandible  to  the  position  of  rest  can  be  followed 
and  the  head  of  the  mandible  located.  It  will  usually  be  found  about 
10  mm.  in  front  of  the  tragus  of  the  ear  and  on  a  line  toward  the  outer 
corner  of  the  eye.  When  located,  mark  the  skin  over  each  condyle  with 
a  lead-pencil  or  chalk,  so  that  the  marks  are  plainly  visible. 

Put  the  trial  plates,  still  fastened  together,  into  the  mouth  and  have 
the  jaws  closed  into  them.  The  stem  of  the  mouth  piece  should  then 
project  forward  in  the  median  line. 

The  face  bow  presents,  on  either  end,  a  sliding  pointer  with  a  clamp- 
ing nut  which  locks  it.     From  the  central  portion  of  the  bow  swings  a 


III.   No.  46. — Location  of  head  of  condyle  on  bone  from  tragus  of  the  ear  to  corner  of  eye.* 


swivel  clamp  pierced  by  a  hole  for  the  stem  of  the  mouth  piece.     This 
swivel  clamp  swings  freely  when  the  set  screw  is  loosened. 

Loosen  the  clamping  nuts  which  fasten  the  pointers,  and  slide  the 
pointers  outward.  With  one  end  of  the  face  bow  in  either  hand  and  the 
bow  projecting  forward,  pass  the  hole  in  the  swivel  clamp  over  the  pro- 
jecting stem  of  the  mouth  piece  and  place  one  pointer  over  each  mark 
locating  the  head  of  the  condyle.  Press  the  pointers  in  firmly  against 
the  face,  and  move  the  bow  to  either  side  until  the  same  number  of 
marks  on  the  pointers  show  between  the  frame  of  the  bow  and  the  face 
on  both  sides.  This  done,  lock  the  clamping  nut  about  each  pointer. 
Support  the  back  end  of  the  face  bow  with  one  hand  in  such  a  way  that 

*  Gysi,   Cosmos,  January,   1910, 


61 

neither  pointer  can  move  from  its  proper  location  over  the  head  of  the 
condyle.  Then  lock  most  firmly  the  swivel  clamp  about  the  stem  of 
the  mouth  piece.  This  renders  into  one,  for  all  practical  purposes,  the 
face  bow,  the  mouth  piece  and  the  attached  trial  plates. 

Or  the  clamping  screw  may  be  given  in  charge  of  the  patient,  with 


III.  No.  47. — Face  bow  in  position  on  patient's  face.     Prothero  attachment  on  face  bow  to  assist  in 
proper  adjustment.     Bites  in  mouth  with  T  piece  projecting  through  swivel  clamp  on  face  bow. 


directions  to  tighten  it  at  the  proper  time.  Then  both  hands  of  the 
operator  will  be  free  to  adjust  the  pointers  over  the  condyles.  (After 
the  patient  has  tightened  the  clamping  screw,  it  is  well  for  the  operator 
to  assure  himself  that  it  is  tight  enough. ) 


62 

To  overcome  the  difRculties  which  some  meet  in  properly  placing  the 
face  bow,  Dr.  J.  H.  Prothero  devised  an  attachment  for  each  of  its  ex- 
tremities which  facilitates  proper  placing.  The  attachment  has  a  slid- 
ing rod  to  enter  the  external  opening  of  each,  ear,  and  screws  by  which 
the  pointers  of  the  face  bow  may  be  raised  and  lowered,  and  moved  for- 
ward and  back. 

The  face  bow,  with  the  Prothero  attachment,  properly  adjusted  to 
the  patient's  face,  may  be  seen  in  Illustration  JSTo.  4Y. 

When  the  swivel  clamp  has  been  locked  in  place,  fastening  the  trial 
plates  immovably  to  the  face  bow,  the  clamping  nut  about  each  pointer 


Protnero  hiiacnmeni 
to  Snow  Face  Bow 


III. 


No  48. — Face  bow  and  properly  articulated  bites  mounted  on   articulator  ready  for  attaching 
models  to  articulator  bows. 


should  be  loosened,  the  pointer  moved  outward,  and  face  bow  and  bites 
removed  as  one. 

The  articulator  may  be  quite  simply  prepared  for  mounting  th©: 
models.  If,  at  some  convenient  place  in  a  bench,  a  nail  be  driven  part 
way  in  and  then  bent  over  in  such  a  way  that  the  lower  bow  of  the  artic- 
ulator slides  under  it  and  is  thereby  held  close  to  the  bench,  the  hand- 
ling of  the  articulator  will  be  made  easier.  By  means  of  the  set  screw, 
adjust  the  model  bows  of  the  articulator  so  that  they  are  parallel.  Slide 
the  lower  bow  under  the  nail  referred  to  and  throw  the  upper  model 
bow  back.  The  pointers  of  the  face  bow  should  be  pushed  in  as  far  as 
possible  and  firmly  locked.    In  the  inner  end  of  each  pointer  is  a  recess 


63 

which  fits  over  a  pin  projecting  from  the  outer  framework  of  the  articu- 
lator joint.  The  face  bow  should  be  spread  a  little  and  the  recesses 
placed  over  the  pins  just  mentioned.  The  face  bow  will  then  be  held  in 
the  proper  lateral  position. 

The  trial  plates  should  now  be  placed  so  that  the  occlusal  surface  is 
parallel  with  the  lower  model  bow.  If  the  steps  so  far  described  have 
been  properly  taken,  it  is  necessary  only  to  move  the  face  bow  up  or 
down  until  the  stem  of  the  mouth  piece  is  parallel  with  the  surface  of 
the  table.  This  brings  the  occlusal  plane  of  the  bite  parallel  to  the  lower 
model  bow.    By  means  of  a  prop,  the  face  bow  is  held  in  this  position. 

To  mount  the  upper  model,  place  it  in  its  proper  trial  plate,  bring 
the  upper  model  bow  forward  above  it,  and  push  the  movable  sleeve  on 
the  model  bow  back  against  the  framework  of  the  articulator.  Attach 
with  plaster  in  the  usual  way,  enclosing  the  forward  end  of  the  sleeve 
in  the  plaster. 

To  mount  the  lower  model  after  the  plaster  attaching  the  upper 
model  is  set,  invert  the  articulator,  face  bow  and  trial  plates.  Place 
the  lower  model  in  its  trial  plate,  bring  the  model  bow  to  position  above 
it  and  attach  with  plaster  in  the  usual  way.  Carry  the  plaster  up  at  the 
heel  in  such  a  way  as  to  include  the  framework  of  the  articulator.  It 
will  then  be  a  guide  in  replacing  the  bow  should  it  be  removed.  Carve 
out  the  plaster  which  forms  the  center  of  the  lower  model,  leaving  the 
ridge  supported  by  the  plaster  above  the  bow.  This  permits  much  better 
access  to  the  lingual  surfaces  of  the  trial  plates  and  teeth. 

The  face  bow  and  mouth  piece  may  be  removed,  leaving  the  models 
attached  to  the  articulator  in  positions  which  reproduce  any  peculiari- 
ties of  the  case.  The  importance  of  such  model  mounting  has  been  men- 
tioned, but  it  is  worthy  of  mention  again.  Whether  or  not  the  dentures 
are  to  be  anatomically  articulated,  the  models  should  be  mounted  in  this 
manner.  And  it  is  probably  true  that  unless  they  are  mounted  thus 
accurately,  articulation  of  the  teeth  to  give  satisfactory  results  in  the 
mouth  will  be  more  difficult  or  wholly  impossible. 


CHAPTER  VII 

DETERMINING  THE  CONDYLE  PATHS 

When  the  models  have  been  properly  mounted  on  the  articulator  by 
means  of  the  trial  plates  and  face  bow,  the  inclination  of  the  condyle 
paths  of  that  particular  patient  should  be  determined.  There  is  some- 
thing of  a  formidable  sound  about  that  term  "  determining  the  condyle 
paths."  It  savors  of  something  that  we  know  but  little  about.  And 
many  dentists  have  doubtless  been  deterred  from  mastering  this  part  of 
the  work  by  the  name  given  to  it. 

But  the  step  itself  is  really  very  simple,  thanks  to  the  mechanical 
appliances  now  available.  It  is  not  more  complicated  or  difficult  than 
the  use  of  the  face  bow.  A  few  words  of  explanation  as  to  why  it  is 
necessary  may  not  be  amiss. 


1^ 


III.    No.    49. — Bite  gauges   as  furuislied  with   articulator. 


All  persons  do  not  chew  alike,  at  least  so  far  as  the  movement  of 
the  condyle  is  concerned.  In  a  few  people  the  condyle  moves  almost 
horizontally  forward  and  back.  In  others,  it  moves  nearly  straight  up 
and  down.  Between  those  horizontal  and  vertical  extremes  there  may 
be  found  in  different  people,  almost  every  degree  of  variation.     The 


■  65 

average  condyle  path  probably  shows  an  inclination  of  33  degrees*  from 
a  horizontal  line,  running  from  the  ear  to  the  nose,  as  in  Illustra- 
tion No.  14. 


III.   No.   50. — Lower  trial   plate  with   "  bite  plates  "   in   proper   position.     Upper   trial  plate  sbowlng 
holes  made  by  cones  of  "  bite  gauges  "  when  protruded  bite  is  taken. 


*  Gysi,   Cosmos,  January,   1910. 


66 

Many  dentists  use  articulators  having  fixed  condyle  paths.  Some 
have  horizontal  condyle  paths  and  others  have  an  inclination  approxi- 
mating 33  degrees.  Articulators  with  horizontal  condyle  slots  are,  in 
the  writer's  opinion^  but  little  better  than  plain  line  articulators. 
Those  articulators  having  condyle  slots  of  approximately  average  in- 
clination are  much  superior  to  those  having  no  such  slots,  or  only  hori- 
zontal ones.  For  many  cases,  articulators  with  fixed  condyle  slots  of 
medium  inclination  will  prove  quite  satisfactory.  They  offer  a  possi- 
ble short  cut  to  the  desired  end  of  good  articulation.  But  for  ipany 
cases  they  must  be  insufficient,  and  one  could  never  know  whether  or 
not  this  was  the  case,  save  as  dentures  articulated  on  them,  fell  short 
of  full  service  in  the  mouth. 

The  practice  of  determining  the  condyle  path  for  each  side  of  the 
patient's  face  is  so  simple,  once  the  procedure  is  understood,  and  re- 
quires so  little  labor  that  it  must  appeal  to  every  ambitious  prosthetic 
worker  as  the  more  desirable  course.*  Furthermore,  one  need  know 
little  of  the  theories  involved,  to  bring  success.  It  is  necessary  only  to 
follow  certain  easy  mechanical  steps  and  abide  by  the  results.  While 
the  determination  of  the  condyle  path  is  here  described  only  in  connec- 
tion with  the  denture  making,  it  is  quite  as  valuable  to  the  crown  and 
bridge  worker.  By  making  full  models  of  both  jaws,  mounting  them  by 
means  of  the  face  bow,  and  determining  the  condyle  paths  of  the 
patient,  the  stress  to  which  the  crown  or  bridge  will  be  subjected  in 
service  will  be  at  once  apjiarent.  And  crowns  or  bridges  may  be  so 
prepared  as  to  avoid  or  successfully  withstand  strains  which,  but  for 
these  precautions,  would  have  been  unrecognized  and  perhaps  fatal  to 
the  piece. 


THE    PROTRUDED    BITE 


With  at  least  one  of  the  articulators  adapted  for  this  work,  there 
are  furnished  two  little  objects  known  as  "  bite  gauges."  See  Illustra- 
tion No.  40.  These  are  useful  in  maintaining  the  trial  plates  in  proper 
relations,  as  will  be  shown.  The  bite  gauges  are  set  into  the  occlusal 
surface  of  the  lower  trial  plate,  as  in  Illustration  ]^o.  50.  When  the 
upper  trial  plate  is  closed  down  onto  them,  the  conical  portions  pierce 
it,  as  shown  in  the  same  illustration. 

*  The  method  of  determining  the  condyle  path  here  described  is  that  used  in 
connection  with  The  Snow  Articulator  and  Face  Bow.  The  somewhat  different 
method  employed  in  connection  with  the  Gysi  articulator  can  be  learned  upon  apply- 
ing to  the  importers,  The  Dentists'  Supply  Company  of  New  York. 


6? 

Both  trial  plates  are  now  placed  in  the  patient's  month.  Before 
closing  the  jaws  together,  the  patient  is  instructed  to  thrust  the  lower 
jaw  forward  about  y^  of  an  inch.  In  this  position  the  lower  jaw  is 
moved  upward  until  the  trial  plates  are  in  contact  anteriorly.     In  the 


III.  No.   51. — Getting  the  protruded  bite.     The  separator  between  trial  plates  at  heels,  as  recorded 
and   maintained   by   the    "bite  gauges,"    is   clearly   shown. 


majority  of  cases  there  will  be  a  greater  or  less  separation  of  the  trial 
plates  in  the  posterior  section,  as  may  be  seen  by  careful  inspection  of 
Illustration  No.  51. 


Here  the  advantages  of  the  conical  upward  projections  of  the  bite 
gauges  are  manifest.  They  preserve  the  separation  betv^een  the  trial 
plates  posteriorly  and  help  retain  them  in  the  proper  forward  and  back 
relations. 

As  soon  as  the  trial  plates  come  together  anteriorly,  staples  like  the 
one  visible  in  Illustration  JSTo.  52  are  inserted  as  there  shown.  A  better 
form  of  staple  can  be  made  by  twisting  two  pieces  of  wire  tightly  to- 
gether and  then  turning  all  four  points  over,  forming  a  pointed  staple. 
It  is  sometimes  advantageous  to  melt  a  little  of  the  wax  of  the  ridges 
about  the  staples,  making  their  retention  more  secure  and  preventing 
any  changes  in  the  relative  positions  of  the  trial  plates.  The  trial  plates, 
thus  fastened  together,  are  taken  from  the  mouth.  By  the  aid  of  a  hot 
spatula  they  should  be  sealed  firmly  together  on  the  lingual  surfaces 
of  the  ridge  at  the  median  line  and  also  at  the  location  of  the  bite  gauges. 
This  prevents  any  motion  between  them  at  the  next  stage  of  the  work, 
and  is  most  important. 


A    SHOET    CUT 


When  it  is  desired  to  dismiss  the  patient  as  soon  as  possible,  and 
to  have  only  one  appointment  previous  to  trying  the  dentures  in,  a 
shorter  method  may  be  used,  producing  the  same  results.  It  is,  how- 
ever, slightly  more  confusing  until  one  is  accustomed  to  the  work. 

To  use  the  shorter  method,  establish  the  "  occlusal  plane ''  as  usual, 
and  trim  the  trial  plates  vertically  to  proper  heights.  Remove  the  lower 
from  the  mouth  and  put  the  bite  gauges  in  place.  Place  the  lower  trial 
plate,  carrying  the  bite  gauges,  in  the  mouth  and  have  the  patient  pro- 
trude the  lower  jaw  and  bite  as  described  above.  With  the  trial  plates 
in  this  position,  any  desired  marks  may  be  made  to  register  their  rela- 
tions ;  but  they  should  not  be  fastened  together. 

The  lower  trial  plate  may  be  now  taken  from  the  mouth  and  the 
bite  gauges  removed.  The  lower  trial  plate  is  then  replaced  in  the 
mouth,  the  jaws  are  closed  together  with  the  lower  properly  retruded, 
and  marks  are  made  across  both  to  show  their  relations.  These. marks 
'should  not  interfere  with  those  made  in  the  position  of  the  protruded 
bite. 

Both  trial  plates  are  removed  from  the  mouth  and  fastened  together ; 
the  mouth  piece  of  the  face  bow  is  inserted  as  before  described,  and  the 
models  are  mounted  on  the  articulator  by  means  of  the  face  bow  and 
trial  plates. 

When  mounting  on  the  articulator  is  complete,  the  trial  plates  are 
carefully  separated,  the  bite  gauges  are  replaced  in  the  spots  from  which 


69 


they  were  taken,  the  spring  of  the  articulator  is  detached  from  the  lower 
portion,  and  the  lower  trial  plate  and  model  are  protruded  until  the  bite 


III.  No.   52. — Side  view  of  trial  plates  following  taking  of  protruded  bite. 


gauges  fit  into  the  depressions  which  they  made  in  the  upper  trial  plate 
when  both  were  in  the  mouth.  The  trial  plates  are  then  sealed  im- 
movably together.  This  brings  the  work  up  to  its  present  stage,  but 
shortens  somewhat  the  length  of  time  the  patient  must  remain  in  the 
office. 


ADJUSTING    THE    CONDYLE    SLOTS 


An  important  part  of  the  joint  of  the  articulator  here  used  is  a  slot 
on  each  side  which  may  be  adjusted  to  any  desired  position  within  a 
considerable  range  of  movement.  The  adjustable  feature  is  controlled 
by  a  set  screw,  somewhat  above  and  behind  each  slot,  which  locks  it  in 
the  selected  position  or  allows  further  adjustment.  A  pin  fastened  to 
the  lower  jaw,  or  mandible  of  the  articulator  fits  loosely  in  each  slot,  and 
may  be  moved  forward  or  backward  the  length  of  the  slot.  This  pin  is 
usually  held  in  the  most  retruded  position  by  the  spring  on  the  back  of 
the  articulator.  In  practical  work,  the  condyle  slot  represents  the  emi- 
nentia  articularis  of  the  skull,  and  the  pin  in  the  condyle  slot  represents 
the  condyle  which  slides  on  the  eminence. 


70 

When  the  bite  was  first  taken  in  the  patient's  mouth,  it  was  with 
the  lower  jaw  in  a  retruded  position.  With  the  upper  and  lower  jaws 
in  this  relation  the  models  were  mounted  upon  the  articulator.  The 
protruded  bite  brought  the  condyles  into  the  forward  position.  In 
order  to  give  this  bite,  the  condyles  were  compelled  to  move  forward 
and  downward  along  the  paths  peculiar  to  that  patient.     In  the  pro- 


III.    No.    53. — Adjusting    the    inclinations    of    the    condyle    slots    by- 
placing  the  lower  model  in  the  lower  bite. 


truded  position  of  the  mandible,  the  flat  trial  plates  showed  a  certain 
amount  of  separation  in  the  molar  region,  and  this  separation  was  care- 
fully preserved  by  the  bite  gauges  used  for  that  purpose. 

The  upper  trial  plate,  with  the  lower  fastened  to  it  as  described 
above,  is  now  placed  on  the  upper  model,  and  by  means  of  melted  wax 
applied  at  the  edge  of  the  trial  plate,  is  fastened  there. 

The  spring  which  holds  the  two  parts  of  the  articulator  in  action 
is  released  from  the  lower  part ;  and  the  set  screws  which  lock  the  con- 
dyle slots  in  position  are  loosened  so  that  the  slots  move  easily. 

The  articulator  with  models  and  trial  plates  attached,  is  now  in- 
verted as  in  Illustration  ISTo.  53.  The  lower  model  is  carefully  placed 
in  the  lower  trial  plate  and  brought  down  to  proper  position  all  around. 

The  bringing  of  the  lower  model  into  its  proper  position  will  re- 


71 

quire  that  the  condyle  slots  of  the  articulator  take  on  a  certain  slant. 
This  slant  will  depend  largely  on  the  amount  of  separation  between 
the  trial  plates  in  the  posterior  section.  Adjustment  of  the  slots  by 
hand  often  facilitates  their  taking  the  proper  slant. 

When  the  lower  model  rests  in  its  proper  place  in  the  lower  trial 
plate  the  correctness  of  the  slope  of  the  slots  may  be  easily  determined. 
Move  first  one  slot  and  then  the  other  gently  from  the  present  position, 
and  note  whether  the  relations  between  the  lower  trial  plate  and  the 
lower  model  are  disturbed.  When  each  step  has  been  carefully  taken, 
any  movement  of  the  condyle  slots  will  be  reflected  in  a  movement  of  the 
lower  model. 

At  that  adjustment  of  the  condyle  slots  which  permits  the  lower 
model  to  rest  evenly  in  the  lower  trial  plate,  the  set. screws  should  be 
turned  until  the  slots  are  immovable. 

There  will  often  be  a  difference  between  the  slopes  of  the  slots  on 
the  two  sides,  one  sloping  more  than  the  other.  If  the  preceding  steps 
have  all  been  taken  with  care,  this  difference  need  cause  no  uneasiness. 
The  same  difference  doubtless  exists  between  the  condyle  paths  of  the 
patient.  It  is  said  to  be  due  to  extraction  of  teeth  on  one  side  of  the 
mouth  before  the  similar  teeth  on  the  other  side  were  lost.  Gysi  re- 
ports having  found  as  much  as  50  degrees  of  variation  between  the 
condyle  paths  on  opposite  sides  of  the  same  face. 

Should  the  articulator  show  a  difference  of  more  than  10  or  15 
degrees  (the  space  between  each  two  marks  on  the  quadrants  over  which 
the  condyle  slots  slide  is  equal  to  10  geographical  degrees),  care  should 
be  exercised  to  see  that  the  adjustments  are  correct. 

Dentists  using  articulators  with  fixed  condyle  slots  will  be  unable 
to  make  this  slot  adjustment.  Such  instruments  are  very  satisfactory 
for  cases  showing  approximately  average  condyle  paths.  But  one  can 
never  know  just  how  great  the  condyle  slope  should  be,  or  whether  a  case 
is  an  "  average  case  "  until  this  adjustment  is  made.  Articulators  hav- 
ing condyle  slots  fixed  in  a  horizontal  plane,  or  nearly  so,  will  be  found 
quite  unsuited  for  accurate  work,  and  dentists  using  them  will  neces- 
sarily confine  themselves  to  setting  up  teeth  for  occlusion,  or  mere  open 
and  shut,  rather  than  for  articulation. 

Having  adjusted  the  condyle  slots  and  locked  the  set  screws,  the 
staples  and  bite  gauges  may  be  removed  from  the  trial  plates,  the  spring 
may  be  engaged  with  the  lower  part  of  the  articulator,  and  the  lower 
trial  plate  pulled  back  to  its  retruded  position. 

The  next  step  will  be  to  carve,  by  the  guidance  of  the  condyle  paths 
as  we  have  adjusted  them,  the  compensating  and  lateral  curves. 


CHAPTER    VIII 


WORKING    OUT    THE    TOOTH    CURVES 


The  inclined  condyle  slots  are  to  be  the  guides  in  working  out  two 
curves  in  the  occlusal  surfaces  of  the  wax  trial  plates.  These  are  the 
curves  which  maintain  the  balancing  relations  between  the  dentures 
when  the  jaw  is  moved  forward  or  laterally.  They  are  known  as  the 
Compensating  Curve,  or  curve  of  Spec,  and  the  Lateral  Curve.  In 
cases  where  the  condyle  slots  are  inclined  but  little  from  horizontal, 
these  curves  will  be  comparatively  flat.  When  the  condyle  slots  are 
inclined  33  degrees  or  more,  the  curves  will  be  found  quite  marked. 

The  compensating  curve  runs  from  front  to  back.  It  is  formed  by 
the  arrangement  of  the  teeth  and  elevates  the  upper  second  molar  above 
the  plane  of  the  anterior  teeth.  See  Illustration  ISTo.  54.  These  curves 
are  usually  rather  flat  in  their  beginnings,  but  if  worked  out  to  an  ex- 
aggerated degree,  often  become  very  marked.  It  is  believed,  however, 
that  nothing  is  gained  by  working  them  out  to  an  exaggerated  degree. 

The  lateral  curve  runs  across  the  trial  plates  at  right  angles  to  the 
compensating  curve,  that  is  from  buccal  side  to  buccal  side.  Like  the 
compensating  curve,  it  is  convex  on  the  upper  jaw.  This  convexity  is 
greatest  in  the  molar  region. 

The  following  methods  make  the  carving  of  these  curves  much 
more  easy  and  rapid  than  formerly. 

Upon  the  occlusal  surface  of  the  lower  trial  plate,  which  was  made 
flat  and  has  not  been  changed,  is  dusted  a  white  powder,  such  as  soap- 
stone  or  talcum,  with  sufficient  evenness  so  that  any  scratches  upon  that 
surface  will  show.  The  trial  plates  are  then  closed  together  and  gentle 
pressure  is  made  from  the  most  anterior  portion  of  the  upper  model  to 


73 

the  most  anterior  jjortion  of  the  lower  model  by  means  of  the  thumb  and 
finger.  By  pressure  on  the  anterior  end  of  either  condyle  slot  the  upper 
model  is  moved  laterally  back  and  forth  several  times.  When  the  trial 
plates  are  separated  it  will  be  seen  that  the  occlusal  margin  of  the  upper 
trial  plate,  on  one  side,  has  rubbed  the  powder  noticeably  in  several 
spots.  If  both  occlusal  surfaces  are  smooth  and  level,  this  rubbing  will 
probably  occur  first  in  the  bicuspid  region.  This  is  shown  by  the  dark 
spot  on  the  occlusal  surface  of  the  lower  trial  plate  at  the  location  of 
the  right  bicuspids  in  Illustration  IsTo.  55. 


III.  No.  54. — The  compensating  curve  and  its  relation  to  the  teeth.* 


The  wax  of  the  lower  trial  plate  is  now  scraped  where  the  powder 
was  rubbed.  For  this  some  workers  prefer  an  old  blade  from  a  safety 
razor,  and  some  prefer  a  wooden  handled  ink  eraser,  such  as  is  common 
in  business  offices.  When  the  wax  in  the  rubbed  area  has  been  hollowed 
somewhat,  fresh  powder  should  be  dusted  on  and  the  rubbing  and  scrap- 
ing process  repeated.  When  the  necessary  technic  has  been  acquired, 
the  scraping  or  carving  can  be  done  rapidly,  since  the  indications  of 
the  first  rubbing  will  prove  a  reasonably  accurate  guide  for  extensive 
carving.  But  it  cannot  be  urged  too  strongly  upon  dentists  who  care 
to  anatomically  articulate  dentures,  that  in  the  first  two  or  three  sets  of 
trial  plates  there  should  be  given  to  this  carving  enough  time  and  atten- 
tion to  demonstrate  the  principles  and  methods  involved.  The  time 
spent  in  doing  this  will  bring  ample  rewards  in  the  future.  Trial  plate 
making  will  never  again  ofl^er  difficulties. 

This  form  of  carving  should  be  continued  on  one  side  only  until  the 
upper  trial  plate  rubs  the  powdered  surface  of  the  lower  to  the  outer 

*  Courtesy  of  Lea  and  Febiger. 


74 

margin  on  that  side.  The  other  side  may  then  be  carved  in  like  manner. 
This  is  as  far  as  this  form  of  carving  should  be  carried,  since  it  is  not 
desired  to  lower  the  labial  margin  of  the  lower  trial  plate.  If  the  trial 
plates  be  now  closed  together  and  examined  from  the  lingual,  it  will  be 


III.   No.  55. — Moving  the  upper  model  laterally  rubs  the  powdered  surface  of  the  lower  trial   plate. 


seen  that  while  the  outer  margin  of  the  lower  trial  plate  remains  un- 
disturbed, the  occlusal  surface  has  been  considerably  inclined  toward 
the  lingual.  This  inclination  will  be  least  in  the  molar  region  and  great- 
est at  the  median  line. 

If  the  upper  model  be  moved  to  the  right  the  trial  plates  will  now 
remain  in  contact  on  the  left  side,  but  separate  noticeably  in  the  molar 
region  on  the  right.  The  amount  of  separation  will  depend  almost 
wholly  on  the  inclination  of  the  condyle  slots.  If  this  inclination  be 
very  slight,  say  only  10  degrees,  separation  between  the  heels  will  be 
slight.  If,  however,  the  inclination  of  the  condyle  slots  be  33  degrees, 
which  Gysi  thinks  is  the  average,  the  separation  will  be  noticeable.  If 
the  inclination  of  the  condyle  slots  should  be  60  or  TO  degrees,  as  is 
found  in  some  cases,  the  separation  will  be  very  marked. 

The  next  task  is  to  so  continue  the  curves  in  the  occlusal  surfaces  of 
both  trial  plates  that  this  separation  in  the  lateral  movement  may  be 


75 

overcome.  This  may  be  done  by  building  up  the  heel  of  the  lower  trial 
plate  into  the  compensating  curve  and  then  carving  the  heel  of  the 
upper  trial  plate  to  fit  the  lower  as  thus  built.* 

The  heel  of  the  lower  trial  plate  is  built  up  as  follows : — Cut  across 
one  end  of  a  sheet  of  base-plate  wax  as  it  comes  in  the  box,  making  a 
strip  about  three-fourths  of  an  inch  wide.  Soften  this  on  one  side  and 
fold,  and  repeat  the  softening  and  folding  until  a  roll  has  been  made 
which  is  soft  all  the  way  through.     With  gentle  heat,  soften  one  heel  of 


III.   No.   56. — Upper  models  moved  laterally  and  pressed  down  on  roll  on  heel  of  lower  bite. 


the  lower  trial  plate,  place  the  little  roll  thus  made  on  the  heel,  and 
attach  it  firmly  by  means  of  a  hot  spatula  thrust  through  the  roll  and 
into  the  wax.  When  the  union  is  sufficiently  firm  for  working  purposes, 
moisten  with  water  the  occlusal  surface  of  the  upper  trial  plate  directly 
over  the  roll.  Before  bringing  the  trial  plate  together,  move  the  upper 
model  about  one-eighth  of  an  inch  toward  the  side  on  which  the  roll  is 
attached.  With  the  upper  thus  moved  laterally,  press  the  models  to- 
gether until  the  trial  plates  come  in  contact  on  the  side  opposite  to  the 
roll.  (See  Illustration  'No.  56.)  Separate  the  trial  plates  and  trim  away 
the  excess  of  wax  to  the  lingual  and  buccal.    It  will  be  observed  that  the 


*  Credit  for  the  following  method  should  be  given  to  Dr.  E.  S.  Ulsaver. 
one  of  the  best  mechanical  steps  in  this  method. 


It  is 


76 

upper  ridge  did  not  flatten  the  roll  horizontally,  but  that  this  surface 
shows  an  inclination  upward  and  backward  from  the  occlusal  surface 
of  the  lower  trial  plate.  This  is  the  beginning  of  the  compensating 
curve.  This  surface  also  slopes  lingually;  that  is,  the  elevation  is  less 
at  the  lingual  margin  than  at  the  buccal  margin.  This  is  the  beginning 
of  the  lateral  curve  in  this  section. 

It  has  been  suggested  that  the  upper  model  be  moved  laterally  only 
about  one-eighth  of  an  inch,  because  it  is  found  that  if  the  model  be 


III.   No.   57. — Bites,  iu  central  occlusion,   kept  apart  by  built-up  heel  of  lower. 


pulled  farther,  the  compensating  and  lateral  curves  are  exaggerated. 
So  far  as  we  are  able  to  determine  at  present,  practically  all  the  benefits 
that  would  be  possible  from  even  the  most  exaggerated  curve  are  secured 
by  the  curve  that  results  from  moving  the  upper  model  one-eighth  of  an 
inch.  Dentists  who  wish  to  carry  their  education  out  in  this  matter 
will  find  it  profitable  to  make  a  set  of  trial  plates  and  in  carving  to 
move  the  upper  model  as  far  laterally  as  the  articulator  permits.  This 
will  give  an  understanding  of  the  compensating  and  lateral  curves  which 
will  be  impossible  of  attainment  by  any  other  means. 

When  the  upper  model  is  allowed  to  return  to  a  position  of  central 
occlusion,  the  trial  plates  will  be  kept  apart  by  the  built-up  heel  of  the 
lower.     (See  Illustration  No.  57.)     At  the  point  of  contact  with  the 


77 

lower,  the  upper  must  be  carved  to  permit  the  trial  plates  to  come  to- 
gether all  around.  Begin  scraping  at  the  buccal-occlusal  margin  in  the 
cuspid  region,  scraping  harder  as  the  heel  is  approached.  The  scraped 
surface  of  the  upper  should  have  just  the  same  upward  and  backward 
inclination  as  the  built-up  heel  of  the  lower.  It  should  have  just  the 
same  lateral  curve,  so  that  in  the  position  of  central  occlusion  the  built- 
up  surface  of  the  lower  and  the  scraped  surface  of  the  upper,  show 
nearly  exact  contact. 

The  heel  of  the  upper  should  be  scraped  in  a  curve  somewhat  longer 
than  that  shown  by  the  built-up  wax  on  the  lower  trial  plate.  That 
probably  extended  forward  only  to  the  bicuspids.  It  terminated 
abruptly,  leaving  a  sort  of  "  jumping-off  place."     The  curve  of  the 


III.   No.   58. 


-The  compensating  and  lateral  curves  so  worked  out  that  the  trial  plates  do  not 
separate. 


upper  necessary  to  fit  the  built-up  lower  may  be  carried  forward  to  the 
location  of  the  cuspid.  When  the  trial  plates  are  in  contact  all  around, 
this  will  leave  a  triangular  open  space  anterior  to  the  flattened  roll. 
This  should  be  built  in  with  soft  wax  and  the  upper  trial  plate  moist- 
ened and  closed  down  on  it.  This  will  shape  it  to  conform  to  the  curve 
in  the  upper. 

If,  by  pressure  on  the  same  condyle  slot  as  before,  the  upper  model 
be 'now  moved  laterally,  a  slight  separation  will  probably  occur  between 
the  heels  of  the  upper  and  lower  trial  plates.     This  is  due  to  the  fact 


78 

that  the  upward  curve  of  the  lower  trial  plate  was  shaped  by  the  occlusal 
surface  of  the  untrimmed  upper.  The  upper  now  having  been  trimmed, 
its  occlusal  surface  occupies  a  somewhat  different  position,  hence  the 
separation.  Another  roll  of  wax  is  attached  to  the  occlusal  surface  of 
the  lower  trial  plate  in  the  same  place  and  in  the  same  way  as  the  first. 
The  occlusal  surface  of  the  upper  is  moistened  and  the  upper  model  is 
again  moved  slightly  toward  that  side  and  pressed  down  until  the  trial 
plates  come  in  contact,  on  the  opposite  side.  This  will  be  found  to  again 
increase  the  height  of  the  heel  of  the  lower  on  that  side  and  to  increase 
also  the  compensating  and  lateral  curves.  The  upper  trial  plate  is  again 
carved  on  that  side  until  proper  relations  are  established.  It  may  now 
be  found  that  when  the  upper-model  is  moved  laterally  through  the  one- 
eighth  inch  of  distance,  the  heels  of  the  two  trial  plates  will  not  sep- 
arate. Should  a  separation  of  any  size  occur,  it  may  be  remedied  by  a 
third  building  in  like  fashion.  By  this  means,  the  compensating  and 
lateral  curves  may  be  so  accurately  worked  out  that  no  separation  is 
perceptible  between  the  trial  plates  through  the  range  of  movement  men- 
tioned. The  trimming  of  the  wax  may  usually  be  accomplished  in  much 
less  time  than  is  here  required  to  describe  it,  and  with  a  little  practice 
the  whole  operation  becomes  very  rapid. 

Meantime,  the  opposite  sides  of  the  trial  plates  have  remained  un- 
touched. Both  sides  should  not  be  put  in  work  at  the  same  time.  That 
is,  if  the  left  side  is  begun,  it  should  be  finished  before  the  right  side  is 
touched.  If  this  is  not  done,  but  both  sides  are  put  in  work  at  the  same 
time,  the  accuracy  secured  by  the  several  mechanical  steps  here  out- 
lined will  be  lost.  The  carving  will  become  merely  time-consuming  and 
vexatious  guesswork.  Before  the  method  mentioned  above  for  working 
out  the  curves  was  devised,  the  writer  has  several  times  spent  an  entire 
working  day  carving  one  set  of  upper  and  lower  trial  plates  to  proper 
articulation.  At  least  equal  articulation  between  the  trial  plates  may 
be  now  accomplished  in  from  45  to  60  minutes. 


CHAPTER  IX 


ARTICULATING    THE    TEETH 


When, the  compensating  and  lateral  curves  have  been  worked  out 
in  the  trial  plates,  the  matter  of  correctly  articulating  the  teeth  becomes 
very  simple,  provided  proper  moulds  of  teeth  are  used.  The  ridge  on 
one-half  of  the  upper  trial  plate  is  cut  away,  beginning  at  the  median 
line.  The  upper  central  on  that  side  is  set  first,  bringing  its  incisal 
edge  in  contact  with  the  incisal  margin  of  the  lower  wax.  If  the  teeth 
have  been  selected  by  the  method  outlined  in  an  earlier  paper,  it  will 
doubtless  be  found  that  this  tooth  will  go  to  place  without  grinding, 
The  rest  of  the  half  set  are  then  placed  in  ^^osition,  in  orderly  sequence, 

In  the  setting  of  the  bicuspids  and  molars,  it  will  make  a  great  dif- 
ference to  the  worker  what  moulds  of  teeth  are  used.  The  bicuspids 
and  molars  to  the  use  of  which  dentists  have,  until  lately,  been  confined, 
are  not  adapted  for  anatomical  articulation,  or  indeed  to  successful  ar- 
ticulation in  any  form.  The  writer  does  not  know  how  lifelike  were 
the  originals  from  which  these  have  descended,  but  certainly  these  now 
bear  no  noticeable  resemblance  to  natural  teeth.  The  relative  heights 
of  the  buccal  and  lingual  cusps  are  far  from  correct,  and  the  cusp  forma' 
tion  in  general  is  not  such  as  to  elicit  the  praise  of  close  observers. 

ISTor  is  it  practicable  for  the  dentist  to  so  grind  these  teeth  that 
proper  articulation  shall  result.  The  proper  articulation  of  28  teeth 
requires  an  accuracy  in  proportion  and  in  cusp   and  sulci  formation! 


80 

which  can  hardly  be  accomplished  by  grinding.  And  even  though  it 
could,  few  dentists  have  the  training,  the  patience  or  the  time  for  it. 
Dentists  who  desire  to  undertake  this  labor  of  grinding  are  referred  to 
the  writings  of  Dr.  George  H.  Wilson  of  Cleveland,  O.,  who  is  very 
expert  in  this  line.  As,  however.  Dr.  Wilson  spends  several  hours  per 
denture  in  securing  these  results,  and  as  all  of  these  results  with  others, 
can  be  obtained  by  the  use  of  anatomical  moulds  in  bicuspids  and 
molars,  it  is  assumed  that  the  dentist  prefers  to  use  these. 

Since  the  introduction  of  the  anatomical  bicuspids  and  molars,  prac- 
tically all  of  this  grinding  has  become  unnecessary.  And  results  which 
no  grinding  is  likely  to  parallel  are  attained  almost  without  labor. 


III.  No.  59. — On  the  left :  wax  trial  plates,  curves  worked  out,  ready  for  setting  teeth.     On  the 
right :    half    of    upper    ridge   cut    away    and    teeth    set. 


The  anatomical  bicuspids  and  molars  are  reproductions  of  the  best 
forms  of  natural  teeth  at  the  period  of  middle  life.  The  mesio-distal 
and  bucco-lingual  proportions  of  the  natural  teeth  remain  unchanged. 
The  buccal  surfaces  are  as  in  the  natural  teeth,  save  that  the  buccal 
markings  in  the  molars  are  accentuated. 

The  occlusal  surfaces  are  changed  from  the  natural  forms  only  so 
far  as  it  is  required  by  the  use  of  two  molars  on  artificial  dentures,  in 
place  of  three  in  the  natural  denture.  The  cusps  show  the  wear  com- 
mon to  natural  teeth  in  middle  life  and  are  lowered  thereby  from  their 
greater  height  in  youth.  This  shortening  of  the  cusps  by  wear  is  a  very 
common  occurrence  in  the  natural  teeth.  The  shortened  cusps  materi- 
ally assist  the  dentist  in  securing  articulation  and  reduce  the  danger 
of  the  dentures  being  dislodged.     Deep  cusps  on  artificial  bicuspids  and 


81 

molars  add  nothing  to  the  effectiveness  of  the  teeth  and  prove  sources 
of  annoyance  to  the  patient. 

The  upper  and  lower  teeth  in  the  anatomical  moulds  are  carved  to 
articulation,  one  with  the  other.  When  opposed,  they  take  their  places 
with  a  definiteness  that  cannot  fail  to  please  one  accustomed  to  the 
uncertain  articulation  of  the  forms  in  common  use. 

These  anatomical  moulds  may  now  be  had  in  four  sizes,  a  small, 
a  small  medium  with  rather  small  upper  molars,  a  medium,  and  a  large. 
Other  moulds  are  in  preparation. 

While  the  artistic  suitability  of  given  moulds  is  an  important  con- 
sideration in  the  selection  of  anterior  teeth  for  any  case,  the  bicuspids 
and  molars  may  be  selected  with  less  reference  to  art.  In  these  teeth, 
the  questions  of  size,  proportions  and  articulation  are  most  important. 
The  bicuspids  and  molars  must  not  be  too  large  to  go  well  to  place. 
They  must  be  properly  proportioned  in  all  their  dimensions ;  and  they 
should  articulate  with  the  opposing  teeth  as  perfectly  as  may  be. 

Practically  all  the  requirements  of  actual  plate  work  may  be  met 
by  the  use  of  a  few  properly  graded  sizes  of  bicuspids  and  molars.  And 
the  anatomical  moulds  as  thus  offered,  carded  with  anteriors  of  suitable 
sizes,  meet  very  well  indeed  the  practical  demands  of  denture  making. 
Moreover,  these  bicuspids  and  molars  are  shaped,  on  the  ridgelap, 
like  half  saddle  back  moulds.  This  makes  them  relatively  shallow.  For 
very  close  bite  cases,  where  little  vertical  space  can  be  had  between  the 
ridges,  the  pins  may  be  bent  upward  against  the  porcelain,  yielding  a 
very  shallow  form  of  tooth. 

When  the  upper  teeth  on  the  one  side  now  "  in  work  "  have  been 
set  so  that  the  occlusal  surfaces  rest  against  the  occlusal  surface  of  the 
lower  trial  plate,  they  should  be  waxed  firmly  in  position  in  order  that 
they  may  serve  as  guides  for  the  movements  of  the  models  in  setting 
the  teeth  on  the  other  side. 

During  the  setting  of  the  upper  teeth,  the  articulator  should  be  used 
as  a  plain  hinge  articulator  and  the  teeth  should  be  set  so  that  all  cusps 
lie  in  contact  with  the  wax  of  the  lower  trial  plate. 

The  other  half  of  the  ridge  of  the  upper  trial  plate  is  now  removed 
and  the  balance  of  the  upper  set,  beginning  with  the  centrals,  is  set  in 
like  manner  as  the  first  half. 

Having  now  set  the  upper  teeth  so  that  they  occlude  properly  with 
the  lower  wax  their  positions  with  reference  to  articulation  may  be 
tested.  Move  the  upper  model  laterally  about  one-eighth  inch  from  the 
position  of  central  occlusion,  and  observe  the  relations  of  the  buccal  and 
lingual  cusps  to  the  occlusal  surface  of  the  lower  trial  plate.  On  the 
side  toward  which  the  upper  model  is  moved,  the  lingual  cusps  should 


82 

be  evenly  in  contact  with  the  lower  wax.  The  buccal  cusps  on  the  op- 
posing side  should  be  in  contact  with  the  lower  wax,  as  should  the 
lingual  cusps  if  the  movement  has  not  carried  them  lingually  off  that 
trial  plate.  When  the  relations  of  the  teeth  arie  satisfactory  in  this 
position,  the  upper  model  should  be  moved  to  the  other  side  and  correct 
relations  between  teeth  and  trial  plate  established.  When  the  proper 
relations  are  assured  and  the  teeth  are  waxed  firmly  in  position,  half  of 
the  ridge  of  the  lower  trial  plate  is  cut  away,  preparatory  to  the  setting 
of  the  lower  teeth. 

As  the  first  molar  is  the  most  anterior  lower  tooth  which  has  two 


III.  No.  60.— On  the  right :  upper  set  all  in  place ;  half  of  lower  ridge  cut  away  and  lower 
teeth  partly  set.  On  the  left :  both  sets  set ;  both  plates  vulcanized  and  remounted  on 
articulator  for  grinding. 


lingual  cusps,  it  is  suggested  that  this  tooth  be  set  first.  With  the  anat- 
omical moulds  used  in  these  illustrations,  the  articulation  between  up- 
pers and  lowers  is  so  exact  that  the  lower  first  molar  goes  to  a  definite 
place  and  lodges  there.  It  should  be  waxed  in  position.  The  lower  sec- 
ond molar  should  then  be  placed  in  position  on  the  wax  and  the  lower 
second  bicuspid  and  first  bicuspid  set.  These  having  been  firmly  waxed 
in  their  proper  positions,  the  other  half  of  the  lower  ridge  is  cut  out 
and  the  same  teeth  on  the  opposite  side  set  in  the  same  order  and  waxed 
in  position.  It  now  remains  only  for  the  dentist  to  set  the  lower  an- 
teriors  in  position  and  in  such  artistic  arrangement  as  he  prefers. 

The  articulation  between  uppers  and  lowers  should  be  made  as  exact 
as  possible  without  grinding  the  teeth.     Because  of  the  correctness  of 


83 

shape  of  the  occlusal  surfaces  and  the  time-saving  method  of  grinding 
to  be  outlined  later,  it  will  be  found  unwise  to  spend  time  in  grinding 
the  occlusal  surfaces  of  the  teeth  in  the  ordinary  manner. 

It  will  doubtless  be  well  to  try  the  teeth  in  the  mouth  and  have  the 
patient  make  the  usual  masticatory  movements.  If  the  foregoing  steps 
have  been  rightly  carried  out,  few  changes  will  be  found  necessary. 

PERFECTING    THE    ARTICULATION 

It  will  be  noticed  that  no  grinding  has  so  far  been  done  to  adapt  the 
teeth  to  position  and  the  time  and  labor  saved  by  this  omission  will  be 
very  noticeable.  The  following  method  for  perfecting  the  articulation 
is  suggested: 

When  the  dentures  are  seen  to  be  satisfactory,  the  upper,  together 


III.  No.  CI. — Anatomical  articulation  in  lateral  excursion  of  tbe  mandible. 
Note  form  of  contact  on   lK)th   sides. 


with  its  model,  is  removed  from  the  articulator  and  vulcanized  in  the 
usual  way.  This  leaves  the  lower  model,  with  the  teeth  in  position,  on 
the  articulator.  When  the  upper  plate  has  been  vulcanized,  it  is  very 
carefully  articulated  with  the  lower,  and  while  so  articulated  is  filled 
with  plaster  and  again  attached  to  the  upper  model  bow.  The  lower 
model  and  plate  are  removed  and  the  plate  vulcanized  in  the  usual 
manner.  It  then  is  carefully  articulated  with  the  upper  which  is  now 
in  its  former  position  on  the  articulator,  and  attached  to  the  lower 
model  bow  in  the  same  way.    A  thick  paste  made  of  carborundum  pow- 


§4 

der  and  oil  is  smeared  over  the  occlusal  and  incisal  surfaces  of  the  teeth 
and  both  sets  are  firmly  rubbed  together  through  every  biting  and  grind- 
ing motion  permitted  by  the  slant  of  the  condyle  slots,  which  remains 
unchanged.  With  the  moulds  of  teeth  here  suggested  the  only  points 
which  will  need  grinding  are  those  which  may  have  received  undue 
elevation  by  the  manner  of  setting  or  by  slight  variations  in  the  flow  of 
the  porcelain  during  baking. 

The  following  advantages  are  gained  by  this  method  of  grinding: — 

The  articulation  is  made  much  more  perfect  than  by  the  usual 

method.     This  form  of  gTinding  takes  down  the  little  contact  points 


III.  No.  62. — On  the  right:  dentures  made  on  a  plain  line  articulator.  They  were  set  with  flat 
occlusal  planes  for  a  patient  having  a  condyle  path  inclined  50°.  On  the  left:  dentures 
anatomically   articulated  with   the  compensating  curve   required  for   the  case. 


which  present  very  close  adaptation.  Many  of  these  little  points  would 
be  difficult  of  location  for  reducti'dn  with  a  stone. 

The  grinding  is  done  more  rapidly  than  in  the  usual  way.  From 
fifteen  to  thirty  minutes  completes  the  grinding. 

The  surfaces  of  the  teeth  are  altered  to  only  the  necessary  extent. 
These  moulds  require  no  general  alterations  to  permit  close  articulation. 

The  glaze  is  removed  from  the  occlusal  surfaces  of  the  bicuspids 
and  molars,  thereby  facilitating  the  retention  and  crushing  of  food. 

The  anterior  teeth  are  automatically  "  aged  "  in  just  tbj  manner 
suitable  to  the  case. 

The  adaptation  of  the  upper  and  lower  dentures,  when  this  grinding 
is  complete,  will  naturally  be  afi'ected  by  the  amount  of  experience  and 
care  of  the  worker,  but  after  a  few  dentures  have  been  made  by  these 
methods,  the  following  adaptations  should  be  present : 

When  the  upper  jaw  is  moved  laterally  so  as  to  bring  the  buccal 


85 

surfaces  of  the  upper  and  lower  teeth  on  one  side  into  the  same  verti- 
cal plane,  there  should  be  contact  of  all  the  upper  and  lower  teeth  on 
that  side  from  the  centrals  or  laterals  backward.  The  interdigitation 
of  the  buccal  cusps  should  be  nearly  exact  and  that  of  the  lingual  cusps 
should  be  sufficiently  close  for  all  practical  purposes.  At  the  same  time 
the  teeth  on  the  opposite  side  of  the  upper  denture,  that  is  on  the  side 
not  engaged  in  rushing,  should  be  in  contact  with  the  lower  teeth  on 
that  side,  from  the  upper  first  bicuspid  back.  In  other  words,  it  is 
possible  to  so  set  the  dentures  that  only  three  teeth  in  the  upper  denture 


w 

^_j  _^^^             ..^ig^.. 

, 

\.         ^ 

\  i 

•WK          Wt 

i^^^,^ 

Q^ 

,-'•- 

"^TO 

Wr'''  -^  ' 

^^^^^^ 

^6^&^m' 

iii 

Pfc^a 

^^t^MUSMB^K^^ 

C 

^ 

III.  No.  63. — Same  dentures  as  shown  in  previous  illustration.  Here  thrown  into  lateral  occlu- 
sion. The  one  on  the  left  is  tilted  to  show  balancing  contact  of  right  molars.  Notice  sep- 
aration between  left  molars  in  dentures  on  right  hand. 


will  be  out  of  contact  while  the  dentures  are  in  this  relation.  These 
teeth  are  the  central,  lateral  and  cuspid  of  the  side  not  engaged  in 
crushing. 

The  adaptation  in  the  incising  bite  is  as  follows.  If  by  even  pressure 
on  both  condyle  slots,  the  upper  model  be  carried  backward  until  the 
upper  incisors  are  in  the  end-to-end  bite  with  the  lower  incisors,  there 
should  be  a  contact  between  each  upper  tooth  and  its  opposing  lower. 

The  upper  cuspids  will  be  in  contact  with  the  lower  first  bicuspid; 
the  upper  first  bicuspid  with  the  lower  second  bicuspid ;  the  upper  sec- 
ond bicuspid  with  the  mesial  cusp  of  the  lower  first  molar;  the  upper 
first  molar  in  contact  with  the  lower  first  and  second  molars  and  the 
upper  second  molar  in  contact  with  the  lower  second  molar.  The  result 
will  be  that  during  the  incising  bite,  when  the  incisors  come  together 
in  the  end-to-end  contact,  the  upper  denture  will  be  supported  through- 
out its  entire  length  on  both  sides  by  lower  teeth.     In  the  final  incising 


86 

bite,  when  the  lower  incisors  pass  upward  and  inward  along  the  upper 
incisors,  the  buccal  cusps  of  each  bicuspid  and  molar  will  slide  down 
the  appropriate  inclined  plane  of  the  lower  tooth. 


III.  No.  64. — Artificial  dentures  in  place.  The  mandible  is  here  thrown  to  the  right, 
bringing  the  buccal  cusps  of  both  sets  into  the  same  vertical  plane  and  interdigitating 
them.  This  relation  is  necessary  for  mastication  and  the  proper  support  of  the 
dentures. 


WHAT  ARE   THE   RESULTS   OF   THESE   STEPS^   AND   ARE    THEY   WORTH    THE 

TROUBLE  INVOLVED  ? 

It  is  difficult  to  compare  these  results  with  those  from  plate  work 
done  in  a  haphazard  manner,  because  there  is  no  comparison  in  the 


87 

value  of  the  service  rendered  to  the  patient.  In  the  ordinary  form  of 
plate  work,  any  real  crushing  or  chewing  ability  which  the  patient 
may  have  is  largely  a  matter  of  accident.  With  the  method  here  out- 
lined, certainty  replaces  guesswork  at  nearly  every  step,  and  in  at  least 
a  very  large  proportion  of  cases,  satisfactory  results  are  assured. 

Patients  for  whom  dentures  articulated  in  the  ordinary  manner 
have  been  removed  and  anatomically  articulated  dentures  furnished, 
have  been  given  much  greater  grinding  power  and  such  greatly  in- 
creased satisfaction  that  one  can  say  only  that  the  average  results  from 
this  form  of  work  are  such  as  could  not  be  attained  in  the  ordinary  way. 
What  is  quite  as  much  to  the  point  is  that  patients  for  whom  dentures 
of  this  sort  have  been  made,  willingly  pay  the  increased  fee. 

The  additional  time  consumed  is  not  as  great  as  would  at  first  ap- 
pear. It  is  probable  that  for  the  average  dentist  the  time  required  for 
making  an  upper  and  lower  denture  will  not  be  increased  more  than 
3  or  4  hours,  when  enough  have  been  made  by  this  method  to  familiar- 
ize him  with  the  technic.  Kapid  workmen  will  greatly  reduce  this 
estimate. 

THE    MAKING    OF    PARTIAL    DENTURES 

It  is  quite  a  common  experience  for  dentists  to  be  confronted  with 
the  problem  of  making  partial  dentures,  involving  the  bicuspid  and 
molar  teeth.  In  such  cases,  as  indeed  in  all  other  partial  dentures,  the 
service  which  the  dentist  renders  to  his  patient  can  be  materially  in- 
creased by  making  models  of  both  jaws,  mounting  them  on  the  articu- 
lator precisely  as  for  full  plates,  working  out  the  condyle  paths  as  sug- 
gested in  the  making  of  bridges  and  the  building  of  a  partial  bite  which 
will  show  the  compensating  and  lateral  curves.  Of  course  in  such 
cases  the  dentist  will  use  the  natural  teeth  opposing  the  trial  plate  as 
the  other  denture,  and  he  will  be  somewhat  limited  by  any  unusual  posi- 
tions which  these  teeth  may  have  taken.  But  allowing  for  such  limi- 
tations, the  stability  and  usefulness  of  the  partial  denture  may  be 
greatly  increased  by  this  method  and  by  so  articulating  the  artificial 
teeth  with  the  natural  teeth  that  the  ordinary  masticatory  movements 
art  provided  for. 

Dentists  are  often  confronted  with  the  request  to  make  one  denture 
to  articulate  with  another  already  in  j^lace.  It  is  unlikely  that  the  den- 
ture in  place  is  constructed  for  anatomical  articulation,  and  it  will 
usually  be  found  impossible  to  anatomically  articulate  another  denture 
with  it. 

Under  such  conditions  the  dentist  is  fully  justified  in  persuading 


88 

the  patient  to  permit  him  to  make  a  new  denture  to  replace  the  one  in 
use.  By  use  of  the  new  moulds  of  teeth  and  the  method  here  outlined 
he  can  then  anatomically  articulate  both. 


III.    No.    65. — Artificial   dentures   in   place.     Teeth    selected   by   tlie   methods   suggested   in 

the  text. 


The  greatly  improved  service  which  he  can  render  with  the  corre- 
spondingly improved  benefits  to  the  patient  are  ample  warrant  for  such 
persuasion. 


CHAPTER  X 

summaky  of  steps   in  anatomically  aeticulating  full  dentures 

Making  the  Trial  Plates. 

Secure  a  good  plaster  model  of  each  jaw. 

Shape  a  base  plate  of  base-plate  gutta  percha  over  each  and  trim 
as  for  a  gold  base. 

With  a  ruler  and  a  soft  pencil,  mark  on  the  side  of  the  patient's 
face,  a  line  from  the  lowest  point  of  the  external  auditory  meatus  to  the 
lowest  point  of  the  wing  of  the  nose.  This  is  the  "  occlusal  plane  "  and 
the  occlusal  surface  of  the  upper  trial  plate  must  be  made  parallel 
with  it. 

Lay  within  reach,  near  the  patient,  a  silver  case  knife. 

Adapt  a  roll  of  soft  wax  to  the  ridge  of  the  upper  base  plate.  The 
base  plate  with  the  wax  ridge  attached  will  be  hereafter  spoken  of  as 
the  "  trial  plate."  Support  in  the  mouth  with  the  third  finger  of  the 
left  hand;  lay  the  blade  of  the  case  knife  from  the  heel  forward  on  the 
occlusal  surface  of  the  right-hand  side  of  the  trial  plate,  supporting  it  by 
pressure  of  the  first  and  second  fingers  of  the  left  hand.  With  the  right 
hand,  move  the  handle  of  the  knife  until  it  is  parallel  with  the  line 
on  the  side  of  the  face.  This  will  shape  the  surface  of  the  wax  ridge 
on  the  right  side,  parallel  with  that  line.  By  the  eye,  trim  the  other 
half  of  the  ridge  of  the  upper  trial  plate  to  the  same  occlusal  plane. 

Trim  the  ridge  of  the  upper  trial  plate  until  it  is  about  a  millimeter 
and  a  half,  1/16  in.,  longer  vertically  in  the  median  line,  than  the  up- 
per lip  at  rest.     Replace  the  trial  plate  in  the  mouth. 

Attach  a  roll  of  soft  wax  to  the  ridge  of  the  lower  base  plate  in  a 
similar  manner,  making  a  lower  trial  plate.  Place  it  in  the  mouth. 
Have  the  patient  close  the  jaws  together,  until  the  lips  touch  lightly  in 
repose.     This  will  give  the  proper  combined  height  for  the  trial  plates, 


90 

and  correct  the  proportionate  height  for  each.  The  cold  and  hard  upper 
trial  plate  will  shape  the  occlusal  surface  of  the  lower  trial  plate  to 
its  proper  plane. 

Mark  the  labial  surfaces  of  the  wax  ridges  for  the  sizes  of  the  teeth. 
Select  the  mould  number  by  the  Twentieth  Century  Method  and  lay 
the  teeth  aside  until  ready  for  use. 

Have  the  patient  bite  both  jaws  together  in  proper  relations  and 
make  continuous  scores  across  the  buccal  sides  of  both  trial  plates  in  at 
least  two  places. 

Remove  the  trial  plates  from  the  mouth ;  put  on  the  models ;  place 
together  in  right  relations.     Seal  together  with  a  hot  spatula. 

Getting  the  Condyle  Paths. 

Locate  on  the  side  of  the  patient's  face,  the  head  of  each  condyle 
and  make  a  plainly  visible  mark  over  it. 

Heat  the  mouth  piece  of  the  face  bow  and  insert  into  the  upper  trial 
plate  in  proper  position.  Put  trial  plates,  fastened  together  with  mouth 
piece  attached,  into  the  mouth.  Adapt  the  face  bow.  Lock  the  bow 
and  mouth  piece  together,  and  remove  all  from  the  face  and  mouth. 

Set  the  model  bows  of  the  articulator  parallel  by  means  of  the  set 
screw.  With  the  articulator  sitting  upright,  slip  recesses  in  heads  of 
the  sliding  pointers  of  the  face  bow  over  pins  on  the  joints  of  the  articu- 
lator. Move  the  face  bow  up  and  down  until  the  mouth  piece  and  the 
lower  model  bow  are  parallel. 

Prop  in  that  position  and  put  upper  model  in  upper  trial  plate. 
Push  the  sleeve  on  the  upper  model  bow  back  against  the  articulator 
frame  and  attach  the  model  to  the  bow  in  the  usual  way,  enclosing  the 
forward  end  of  the  sleeve  in  the  plaster.  Invert  the  articulator,  face 
bow  and  trial  plates ;  attach  the  lower  model  in  the  usual  way,  carrying 
plaster  up  about  the  base  of  the  articulator  frame.  Before  the  plaster 
is  too  hard,  cut  out  the  center  of  the  lower  model. 

Mount  the  bite  gauges  in  the  occlusal  surface  of  the  lower  trial 
plate.  Put  both  trial  plates  into  the  mouth.  Have  the  patient  protrude 
lower  jaw  and  bite  until  trial  plates  come  in  contact  in  front.  Fasten 
together  with  staples  at  region  of  cuspids,  and  seal  together  on  the  lin- 
gual sides.  Loosen  the  set  screws  governing  the  movements  of  the  con- 
dyle slots.  Mount  upper  trial  plate,  with  lower  trial  plate  attached, 
on  the  upper  model,  and  seal  fast.  Adapt  lower  model  to  rest  quietly 
in  lower  trial  plate  and  lock  the  set  screws  and  condyle  paths  in  the 
slant  which  permits  this  position  of  the  model.  Remove  staples  and 
bite  gauges.     Engage  the  spring  on  the  back  of  the  articulator. 


91 

Cakving-  the  Compensating  Curves. 

Dust  white  powder  on  the  occlusal  surface  of  the  lower  trial  plate. 
Move  the  upper  trial  plate  laterally  on  lower,  and  carve.  Attach  a 
conical  roll  of  wax  to  heel  of  lower  trial  plate.  Pull  the  upper  model 
to  that  side  1/8  in.  and  close  till  trial  plates  are  in  contact  on  the  oppo- 
site side.  Trim  away  the  excess  buccally  and  lingually.  Carry  the 
slope  of  the  flattened  roll  into  the  occlusal  surface  of  the  lower  trial 
plate  at  cuspid.  Trim  upper  trial  plate  to  fit  lower  all  around  when  in 
central  occlusion.  Repeat  once  or  twice,  until  the  heels  remain  in  con- 
tact during  lateral  motion  toward  that  side.  Build  the  other  side  in 
the  same  manner. 

Aetictjlating  the  Teeth. 

Cut  away  half  of  the  ridge  of  the  upper  trial  plate.  Set  half  of 
upper  set  of  teeth,  beginning  with  the  central.  Set  occlusal  surface  of 
bicuspids  and  molars  against  occlusal  surface  of  lower  trial  plate,  as 
carved.  Either  purchase  the  anatomical  moulds  which  permit  this  or 
grind  the  teeth  until  it  is  possible.  Wax  the  teeth  firmly  in  position. 
Set  the  other  half  of  the  upper  set  beginning  with  the  central.  By 
lateral  movements  of  the  upper  model,  make  sure  that  the  buccal  and 
lingual  cusps  follow  the  occlusal  surface  of  the  lower  trial  plate  prop- 
erly in  lateral  and  biting  movements. 

Cut  away  half  of  the  ridge  on  the  lower  trial  plate.  Set  lower  first 
molar,  second  molar,  second  bicuspid  and  first  bicuspid  on  one  side  in 
the  order  here  named.  Do  the  same  on  the  other  side.  Fill  in  the 
anteriors  to  articulate  properly  and  give  natural  effect.  Perfect  articu- 
lation as  far  as  possible  without  grinding. 

Try  the  articulated  teeth  in  the  mouth.  Eeplace  the  lower  plate 
on  the  articulator.  Detach  the  upper  model  and  vulcanize  the  upper 
plate  in  the  usual  way.  After  vulcanizing,  articulate  the  upper  plate 
with  the  lower  which  is  still  on  the  articulator  and  again  attach  the 
upper  to  the  model  bow  in  that  position.  Vulcanize  the  lower  plate; 
articulate  it  with  the  upper  plate  and  attach  to  the  lower  model  bow. 
Place  a  paste  of  carborundum  powdei'  and  oil  on  the  occlusal  surfaces 
of  the  teeth,  press  the  plates  together  and  move  them  through  all  the 
movements  possible  to  masticating  and  biting. 

For  partial  dentures,  work  out  the  trial  plates  to  the  best  possible 
articulation  with  the  opposing  teeth  and  set  the  artificial  teeth  accord- 
ingly. For  bridges,  work  out  models  exactly  as  for  partial  dentures. 
Shape  occlusal  surfaces  of  dummies  so  as  to  avoid  destructive  or  undue 
lateral  strains, 


COLUMBIA  UNIVERSITY  LIBRARIES  (hsi.stx) 

RK656C532C.1 

Mechanical  side  of  anatomica  articya^^^^^ 


2002449552 


